The benefits of FF for professionals who require the highest image quality are obvious.
How ever there are down sides... that few FF lenses are anything like telecentric causes problems in the periphery of images. Mostly FF cameras are much larger than APS, and not every one sees that as an advantage in private life.

I feel we are waiting on the same sort of revolution that the OM1 brought to 35mm film cameras... a reduction in size and weight with out reducing quality and at the same time re setting the standard for viewfinders, and also the need to solvin the telecentric lens/sensor problems.

For this to happen there will have to be an a revolution in sensor design... most lenses will need to be redesigned...
... software will need to be developed to automatically overcome residual problems.

I can see FF cameras being redesigned with the same considerations given to those problems solved in the 4/3rds system, but somewhat larger in size.