I'm a little out of my depth here, but unless I misunderstand you, I think you're ignoring the fact that if they have better tech to put into an SLR-lite package, that tech exists to be put into a real SLR as well. And people aren't paying several times as much for SLRs now just because they have too many hundred dollar bills to fit in their wallets.

Also, in regard to the sensor being exposed, there's no reason a future SLR body couldn't have a shield that comes down when changing the lens.