I think the days of the SLR are numbered. With digital there is no longer a reason for that big mirror flipping up and down.
Also leaving that big mirror box off will make them more compact. Probably back to the size of the old 1930s era Leicas.
Mine is mirror-less and smaller than the typical DSLR.
I agree about the DSLR is slowly going away.
I went with the GH4 because it was an affordable 4k body.
Micro four-thirds and APS-C mirrorless cameras do a great job and are way more practical than their DSLR big brothers. Love taking my Canon OM-D on excursions.