Just for info, I made a decision over Christmas with my gear, in that my Nikon Z system will be my primary wildlife / birding system as I already have the Z8 & Z9, as well as as the Z 100-400, 400mm F4.5, 1.4x converter, 180-600, and 500mm PF (F mount lens). So I have a good list of long lenses. Therefore my Sony A7RV, will be my landscape / Portrait main body, which means my A6700 and the new A7C II will be my everyday carry / holiday bodies.
Regrettably I think that means the end of the road for my Micro Four thirds system which I've used for over a decade (which I'm just not using anymore). As good as it is (and it is a really nice system), it's now not really that much smaller or lighter than an A6700 / A7C II body with the 24mm and 40mm pancake lenses. Also, if you look at my OM-1 with the 12-40 (24-80mm) F2.8 standard lens and compare it to an A7C II with my Sony 20-70 F4 G then the Sony setup is only 21g heavier and a very similar footprint (1002g vs 981g).
When it comes to wildlife, I can already get to 900mm in 20mp APS-C mode on the Nikon Z8 / Z9 and the 180-600mm (or maybe soon the 600mm F6.3), and to match or beat that focal length that I'd most likely need to get the big white (the Olympus 150-400 (300-800mm effective) and engage the 1.25TC for 1000mm @ F5.6 (only a 1/3 of a stop brighter), and that lens is over £6k new. By all accounts a truly stunning lens but at £6.5k not cheap and also not small. Also size and weight wise the Olympus Combo is only 380 lighter than a Z8 with the 180-600 or actually 94g heavier if I replace the 180-600 with the 600mm F6.3 which I'm considering.
I know these aren't a direct comparison as each model has it's own benefits / features that the other doesn't, but to be honest I don't need the speed of the OM-1 (20fps in Raw+JPG is fast enough for me that both the Nikon bodies will do with an unlimited buffer), so I think it's time to retire the Olympus system altogether. I'll either see what I can get for them and sell them, or if the prices are really low just keep them as back up but will most certainly pair down the lens collection to the bear minimum. It's a shame but two systems is a luxury and 3 systems is just silly.
Also, and not really a major contributing factor, but I just don't see much development by OM Systems in the last couple of years into a new high end body to compete with the APS-C and FF bodies which are getting closer in size, speed, IBIS capabilities etc but with much more room for cropping with their larger sensors, and better high ISO performance (which by the way the OM-1 is no slouch at). I can see why a lot of people still love M4/3, and if it was my only system I'd be perfectly happy and make it work for me (as I did), but as I'm very fortunate to be able to spend money on my hobby and have a really nice Nikon and Sony system as well, like I say, one of them has to go, and I think it's going to be the Olympus system.