Already we see 10-12-16 mp cameras exhibiting the shortcomings of current glass. It is a real problem when resolving power outperforms glass and in doing so sometimes creates some fairly significant "new" photographic challenges.
I question if makers will ever create glass, at acceptable prices, that won't marginalize current or higher available resolving power.
Yes I agree whole-heartedly that where we are today with lens and sensor design gives us a real-world situation where MPs beyond the mid-teens are superfluous.
But hey, this is a "future of DSLRs" thread and we are speculating...
Maybe the future of DSLRs is better glass, bigger sensors, in bodies roughly the same size as todays full-framers. Given that the Canon EF mount can already support an image circle of around 46mm (remember their tilt and shift lens series) maybe the real leap in resolution will come from a new crop of top-end lenses with larger image circles and a bit of tweeking to the physical layout of the bodies / more miniturisation of components and power sources; you never know. Given that the commercial photographers using 1dsIIs and are now being courted by hassleblad/imacon, Canon might want to keep this market segment, given that it has been extra business on top of their pre-digital sales, where 35mm was not as big a part of the commercial scene as was medium and large format film.
And of course I don't want more res without better DR and better colour reproduction. Keep working at it Fuji and Foveon.
Whether this would come at acceptable prices– if history is a guide, it will just be a matter of time.