This is getting interesting, at least for those high pixel counters. But for most amateurs it won't be a game changer since I suspect the price is going to be in the "Leica" Range.
As far as I'm concerned, the only good thing about this is that cell phones cameras might not kill the DSLR market.
We now have talk of Sigma making bodies as well as lenses, three ranges of bodies, three ranges of lenses and three R&D departments working on the same mount and system.