The rumor mill grist is saying that we will see a 50-megapixel Canon DSLR announced sometime soon, with Nikon and Sony slated for same.
It is fallacious to assume that the only value of more megapixels is more resolution (and it often might not be more, since the demands at every level of the combined photographic system have to be optimal).
I’ve written exensively on oversampling in the past, and I firmly believe that 50 megapixels is a worthwhile advance (72 or 144 would be even better). All things being otherwise equal, a 50MP sensor is going to produce significantly better images than a 36MP sensor for the same print size, or if downsampled from 50 to 36. All sorts of factors come into play however, so the devil is in the hardware and software implementation details, but if recent advances offer any guidance, 50 will be looking very fine indeed.