The real big improvement in newer sensors, like stacked sensors, is faster readout speed. So M43 may move from 60fps (which is already ahead of many formats) to 120fps sensors. But given you deleted all the parts about speed, you seem to not care about that aspect.
OK, let's talk about your speed fanaticism.
And the fact that the fastest DILC camera out there, if you do the math...is now a
full frame Nikon, processing a sensor with
four times the surface area and twice the resolution.
The new Nikon Z9 does 20fps with autofocus at 45.7mp, or 914mp per second in RAW. The Sony A1 does up to 30fps, but only with e-shutter and lossy RAW, at 50mp, or 1500mp per second; 10fps with mechanical shutter and lossless RAW at 50mp, or 500mp per second.
The Olympus EM1x does 18fps with autofocus but e-shutter at 20mp, or 360mp per second. With mechanical shutter it does 10fps at 20mp, or 200mp per second. The Olympus' EM1x quotes up to 60fps with e-shutter and locked autofocus, 1200mp per second, but a figure of little real-world consequence when shooting the EM1x's intended subject, wildlife and sports as locked AF doesn't keep your moving subject in focus, does it?
Plus, PLUS, the first DILC to go fully digital readout, no mechanical shutter...is, again, a Nikon
full frame camera with
four times the sensor surface area to read, over twice the resolution.
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We've been WAITING for the all the promises that they made when choosing the smaller sensor to actually be fulfilled. They promised the best speeds, smaller bodies and lenses (they did indeed fulfill the lens part) and performance not really limited by the smaller sensor.
In the real world, they continued to put a 16mp CDAF sensor into bodies way past its sell-by date.
It is reasonable to believe that you, like most people, don't come into contact with many other people using their cameras. I, on the other hand, both live and work in tourist districts, and I see EXACTLY what is going on in the photography business by simply looking around me and seeing what people are carrying. And it was a hard sell on a 16mp CDAF camera (Olympus EM5 mk2) when competitors were selling 24mp PDAF DSLR with Live View and better low light capabilities (Canon T6i / T6S).
It is personally very frustrating to see the HORDES of Canon Rebel users holding their cameras out at arms length, using Live View, to take their photos. The vast, vast majority of them use it that way. I want to yell "Get a real Live View camera if that's the way you want to use it!!", but of course that would be rude. But they bought a camera that can, generally, do more than the m43 competitor (yes, yes, you yell "but IBIS!!" as if that's the Holy Grail. It's only one of a number of features that must be weighed) at the same price (for example, generally hit focus with far more consistency, not to mention better low light abilities).
I could go on, but sadly you believe you are correct, that m43 is such a great system as it stands - yet, Olympus BAILED OUT of the business. There is nothing wrong with the format, the
problem is 2 manufacturers that have rested on their laurels and not pushed the designs enough, and now the competition is meeting their design paradigm (mirrorless), and trampling all over them with technological advancements.
