A good update from the Mark II would be about the only way Canon could separate me from some money right now. I don't have any complaint with the autofocus, so I don't know that I would notice whether it had DPAF. I don't want a slower lens with greater zoom range, like the direction Sony went with their vaguely comparable model. IQ is fine for what I post to the web and the 13" x 19" prints hanging on the walls of my home. ACR does fine with the lens corrections. I don't need more MP, and wouldn't want to trade off something else to get more. But all that said, I certainly wouldn't object if they upgraded quality without sacrificing things I find useful.
I don't need built-in GPS or 4K video, but either would help sway me toward upgrading. I have paired the camera with my iPhone so that GPS is stored with the pictures when taken. But rather than eating up battery on two devices when I'm out for a day of sightseeing, if I want to note exactly where some pictures were taken, I'll take a shot with the phone, and its GPS data will tell me where I was at that time of day.
I've not had a problem with dust or sand with my II. When I pack it in a bag, I put it in a little case, but out sightseeing, I don't bother with the case, and just put it in my pocket when not in use. I've used it at beaches but not out in deserts, though.