Given that the most widely used (*statistic I just made up, at least most number of manufacturers that are compatible with each other) is the Arca-Swiss-style plate/system, I definitely wouldn't complain if the 7D mk2 comes out with inbuilt rails along the base.
But then you have manfrotto, probably one of the biggest/popular manufacturers, and they're not arca-compatible. Hell, they're not even compatible with their own systems because they've got quite a few systems themselves that aren't compatible with each other. Imagine the complaints coming from manfrotto and manfrotto fanboys if the next dslr has A-S rails. (and other manufacturers too, Gitzo do their own plate-mounting system don't they?)
How about AdamJ's suggestion of a brand-new type of plate? cue the complaints from A-S and manfrotto fanboys (although it was technically a good suggestion, it just won't work in the real world).
Hell, i'd be happy at least with just a camera with two 1/4" threaded holes, make them a standard distance like 20mm apart or so.
- Anyone with old tripod equipment can just pick one hole or the other and it works perfectly fine.
- Any future plates from Kirk, RRS, Manfrotto, Gitzo, Joby, whoever, can either stick with using 1 hole (custom-fitted RRS/Kirk plates can easily get away with 1 hole because they hug the body),
- or they can use the 2-hole mounting method, completely anti-rotation even using a flat generic (non-custom-camera-fitted) plate.
- Probably the only thing I can think of is the (slight) increase in camera size/weight to fit in the extra hole.
- Getting everyone on board to agree on how far apart the holes should be, you know at least one company won't play along and will make them 15mm or 25mm apart when everyone else is using 20mm (think Olympus sticking to xD cards, or Sony to MS, eventually they came around though).