Is m43 actually used by many pros? If it can't compete on IQ or size I don't know why you'd actually pick it as a pro. For mere mortals the size advantage of the smaller cameras and lenses along with OBIS is important and I get that, but I don't really get where these bigger m43 cameras fit in for pros - the lenses aren't even cheap.
I can't think of any occasion I've seen a paid photographer not using a DSLR.
The IQ differences are much smaller than you might think, the m43 cameras happily give a Canon APS-C DSLR a run for their money and I see plenty of wedding togs using a Canon 600D etc. I also see some wildlife togs using M43 setups since you need the reach.
I agree the market is probably pretty mall for such cameras and I also don't really see the point. I have a little Olympus EPM-2 and I love the results it provides in a tiny package.
I'm also not really sold on the idea of the f/2.8 lenses. Yeah, they are way smaller than the 24-70mm or 70-200mm f/2.8 FF lenses but they don't have the same equivalent aperture. Its those tiny fast primes that are more interesting, or the incredibly light plasticity kit lenses.