Just a quick walk through history...
When Canon announced the 5D2 many years back, people claimed (i) they have no need for sensors with more than 12 MP (ii) lenses won't be able to support such a 22 MP sensor (iii) diffraction would kill the usefulness of such a sensor. The 5D2 turned out to be a massive success for Canon.
When there are rumors about Canon releasing a 22 MP FF camera after Nikon's 36 MP D800, people claim Canon is falling behind, and they are going to dump all their Canon stuff for the exciting D800.
When there are rumors about Canon releasing a 45 MP FF camera, people claim lenses won't be able to support the sensor. No more talks about diffraction. No more talks about the uselessness of sensors with more than 12 MP. After all, there's a 36 MP D800 is on the market.
How very interesting.