As far as image quality is concerned, there's still argument that digital has yet to achieve the 'ultimate' IQ that film might... its just a question of cost and convenience....
'Consumer' film cameras were headed down that avenue for decades before digital, with ever smaller and cheaper film cameras, coming down from 10x8" plate cameras to 120 roll-film, shrinking to movie-format 35mm and beneath that to 110 cartridge, and then competition to maximise the area under the curve of the compromise, with 'better' lenses and stuff used to compensate for the smaller film.
Polaroid was probably the most intriguing leap forwards in halide photography, the film 'self-developing' to direct print. Mass market scale was employed to sort of keep costs reasonable, but 'consumer' grade cameras offered it at the expense of IQ, whilst pro grade MF cameras got some back at extra cost.
So, where could halide photography have gone, that it actually didn't? Most things were and still are possible, its just whether the 'market' will buy it.
Analogue electronic cameras existed.. as said they were Video cameras, and they were on the high-street, in volume by the 1980's, probably the height of popular film photography... they just didn't make 'stills', very often... but then did the market want them? Back to that area-under-the-compromise-curve... cost vs convenience vs quality.
Digital, and the proliferation of consumer electronics gave huge advantage to digital-photography to start exploiting some of the convenience benefits over halide film.... B-U-T... what has mostly promoted wide-spread uptake of digital photography, I think, is the Smart-Phone.
Go back quarter of a century and there were digital cameras. Go back twenty years and they were on the high-street, and not so exorbitantly expensive.... But, I remember showing my Gran my first one, and she was perplexed, peering at its postage stamp sized back-screen, as to how and when she could see the 'Prints', and when trying to explain that I didn't have to get the 'film' developed, asking how I could plug it into the TV then?
What has pulled the more wide-spread adoption of digital, then has been the wired world, and the fact that now, I could take the SD card out of my camera and slot it in the side of a TV to show her the pictures, or, I can e-mail them, or post them on farce-broke..... Digital photography has evolved and been adopted to fit with digital, well, LIFE really.
IF the internet hadn't evolved the way it has, if digital consumer devices hadn't evolved with the amount of convergence it has, with transmission and distribution and display of media on electronic devices... 'Consumer' digital photography probably wouldn't exist.
So if Digital photography hadn't evolved, would there have been anything to 'drive' any significant evolution of halide film photography in any particular direction?
The APS Advanced-Photo-System, as the last real development in pre-digital film-photography, sort of suggests where evolution may have gone...
And an interesting case study; the system was developed to try and offer something that was better than the very small format 110 cartridge, and cheaper than 35mm, but curiously as much as anything, the imperative was pandering to the environmental lobby, where the smaller film area, begged less chemicals to make and develop, hence less pollution, the same imperative that saw the evolution of Dry-To-Dry processing systems and the mini-lab.
Technology does not evolve in isolation... its cause and effect at every stage.
I like motorbikes.... its almost utter serendipity, though that any-one ever built one! I mean, you want to make a self propelled vehicle? WHO in their right minds starts with something with just two wheels that will fall over! You give it three or four so it doesn't And you give it more than one seat, so you can carry a passenger or three. In fact, you build a TRAIN.
The motorbike exists, because when Gottenlib Daimler unbolted one of his bosses gas-engines from the bench and took it out-side and got it to run on furniture polish..... it wasn't powerful enough to pull anything bigger or heavier than a kids hobby-horse that was lying around, hence Einspur, the first internal combustion engine vehicle! And later pioneers, faced with similar problems and dilemmas, came to the same conclusion, and strapped small De-Dion engines to push-bikes!
Fact that they existed was some-what serendipitous, too! The hobby horse evolving out of a stick with a stuffed toy horses head on the end, used in masques re-enacting jousts, and given to the kids to play with! Becoming the hobby-horse when the grown ups decided to have drunken races around the lawn after the kids had gone to bed, and boys being boys wanting a better hobby horse for the next party, culminating in the penny-farthing.... along the way, the 'in tension' wire spoked wheel evolving in favour of the 'in compression' wooden spoked wheel; the chain drive being adopted from a sewing machine, the innovation of the india rubber tyre, that developed into the pneumatic tyre.... one advance begged by another.
The precept, how would film photography have evolved if digital hadn't, is like most historical 'What ifs'.. what if Napoleon had won at Waterloo? What if Margret Thatcher had backed down to the miners? What if Harold Hadrada had cornflakes for breakfast instead of Kippers? So much is down to fluke, chance and serendipity.... leading into the very very esoteric science of 'Chaos-Theory' and the suggestion that any apparently chaotic or unpredictable situation, regardless of the statistical im-probability will have a tendency to trend to a statistical probability... and we start getting very Douglas Adams, that suggests that ultimately there's no escaping fate, and what will be will be, and that really there isn't a historical alternative, all roads lead to Rome, and whatever the what-ifs, nature would have its way and it would get to the same place one way or another regardless..... At which point the philosopher pointed to the Babel-Fish and promptly dissapeared in an ethereal puff of logic.....
Where could film have gone?
Well, environmentally unfriendly, it PROBABLY wouldn't have gone anywhere! As regulation started to bite, like with cars being dogged by emission controls, its only the now very very limited use of film and all the necessary use of the associateted chemicals that keep the environmental impact within tolerable limits to the regulators. The market saturation and wide-spread adoption of consumer cameras, probably wasn't sustainable, anyway, and that market would have been under pressure to shrink, without the alternative of digital being there to take up the demand.
The market had already concluded an 'acceptable quality level' centred somewhere on that of 35mm, and if you wanted 'better' it was already there in Medium Format, but at a price not many were prepared to pay. If you wanted cheaper or more convenient, that too was already there in 110 cartridge instamatics, but the mass market had centred on 35mm, as 'good enough' for most and a pretty good area under the curve compromise.
Evolution that was taking place in the last high-street film cameras, was significantly an increase in 'automation' such as auto-focus, and the compromise smaller format APS film, between 110 cartridge and 35mm... but that was probably a bridge too far for most, and didn't offer enough area under the compromise for many buyers, and never gained the take-up to garner the economies of scale that 120 or 35mm or 110 cartridge did, even before digital reared its head.
Personally, then? I think that the market would have shrunk. As a luxury product you don't really need, the consumer would not have demanded much more of the manufacturers, and certainly not been prepared to pay much for anything they did develop. Enviro regulation would have bit, and the pressure on the market would have seen popular photography probably shrink, and manufacturers loath to invest in development, leading to a stagnation, and likely 35mm film continuing the accepted norm, with escalating costs as the market shrank.
Evolution of analogue electronic cameras, would probably have continued, but, as video cameras not stills..... again, technology does not evolve in isolation... so, with VHS-C tape sort of setting the bench mark for the acceptable quality level and size of the device? Without 'Digital' computing driving the evolution, and mass market economies to develop the 3.5" floppy diskette, let alone large capacity hard drives, or flash-drives? Where would the 'pull', the necessity is mother of invention, come from to evolve analogue electric photography in ANY direction? It was there, but peculiarly restricted to video, not stills, and even there, it was probably close to saturation and not gone much further, were it not for digital.