To me, the milc cameras are like the viewfinder cameras of the 60's.
Lots of people had one for carry-everwhere, including kids, yet big, clunky SLR's still sold well as did mf cameras.
I remember as a kid that it wasn't unusual to see advanced amateurs walking around with a Hasselblad or Bronica, but most photographers had an SLR around their necks.
Rangefinder cameras back then were actually easier to focus than SLR's as they had split image focussing, yet even with cameras like Leicas, the SLR was still king, and regardless of how good milcs become, they will NEVER completely replace DSLRs.
A modern milc is a very good and practical camera for 90% of people.
However, for people who really want speed, ergonomics and ultimate quality, you can't beat a DSLR.
There are also many people who would be happy with a milc, but want to look like they are serious, so the just HAVE to have a DSLR, even if it's just a low-grade Rebel.