More to the point, why aren't you discussing whether or not we've reached peak image quality?
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I suspect as time goes on there will continue to be incremental improvements in ISO performance, dynamic range, resolution, etc. Perhaps also improvements to file types to reduce compression loss, to make file sizes more manageable as the resulting pixel count continues to grow?
It's probably hard to imagine something much better than the Nikon 850, top of the range Sony mirrorless, etc. but it will be out there eventually. Who knows, in 20 or 30 years time zooming in to 400% may look like 100% is now in terms of image resolution and detail?
Also I think further improvements to features such as focus point selection and distribution across the viewfinder/screen will occur. Perhaps even a return of eye controlled focus point selection too, so you have the option to just look where you want to focus, instead of joysticking or button scrolling?
I think camera manufacturers are going to have to keep improving and innovating if they are to keep the market alive against competition from top-end smart phones. That's already pretty much killed the 'point and shoot compact' end of the market, and multi-lens smart phones are now eating away at the entry level DSLR and mirrorless end of the market. If manufacturers don't keep working to raise the bar with better image quality for enthusiast and pro grade cameras, then I don't think they'll survive.
I take the point about 'how good does it need to get', after all, digital cameras from 10 or 20 years ago can still produce some very nice looking photos, until the light gets tricky and/or you zoom in to the image, then the difference becomes apparent.