That's not because of the cameras being mirrorless; it's because (for Canon anyway) they purposely gimp video on their DSLRs to get you to buy their Cine-EOS cameras.
Strides which do not result from them being mirrorless.
You should understand that the mirror does not get involved at all when doing video with a DSLR.
So, all of these 'strides' can and have been replicated in the next version of the cameras.
I'm not sure what your point is - it's mirrorless that have really pushed the tech on here at least at the cheaper end of the market. It's my understanding that Lumix G range for example has been widely adopted for video in a way that SLR has not. Are you saying these users will defect to SLR with a new generation? Can't really see why, since all that going SLR would do is introduce some extra mechanics they don't need.