IF it delivers image quality equal to Nikon D4s
AND IF Sony has improved AF performance notably
AND IF it had a better battery holding charge for 500 shots
AND IF it cost 999,- including dual-lens kit 35/2.8 + 55/1.8
THEN I would buy one ...despite all the useless 4k cr*p in it.
The way it is .. a 4k camera that cannot record 4k in-camera, wheras a tiny GoPro can do that ... well, I don't know ...
What I do like however is Sony giving their customers a choice: one does not have to purchase "the video-optimized model" just to get a decent sensor or otherwise attractive stills features. Canon only offers some of that choice at 1D-X and 1D C price levels.
A7/R/S ... strategywise exactly what I would like to get from Canon. A very compact, decent mirrorless body in 3 implementations:
1) mid-rez sensor, really HI-ISO, 6+fps, no video other than liveview feed fppor EVF ... 5D IV
2) hi-rez sensor, 5fps, no video other than liveview feed for EVF ... 5D-R ["Resolution"]
3) low-rez sensor, video-optimized model ... 5D-C ... with zebra and peaking and quadrophonic microphones and HUGE rigs and follow focus gears on top of autofocus ... plus all that other stuuf all tjose videots are constantly clamoring for in stills cameras.
Of course the last version would be most exepnsive and the first version cheapest. :-)