I'd like to see a 7D mk II with lower noise at all ISOs, same resolution (18 MP = fine for me), some AF tweaks maybe.
Canon, even though I don't use video much, if you could allow it to have full time AF while recording that would be good (and I'd use video more). Maybe a swivel screen to help filming bur more-so, for live-view / macros at odd angles!
My 7D serves me very well... I really don't need more than 7 or 8 fps (I like the 3fps and 8fps options). What would be handy is more than 3 bracketed exposures (eg up to 7 or 9).