Eventually solid state will likely replace most spinning media. The amount of time between now and then depends on a number of factors, including cost curve, reliability, and density.
I do like that Apple took the chips out of the archaic HD module. In the near term, I can understand the value in making SSDs emulate spinning hard disks, but long-term, it seems pretty silly to force chip memory to emulate a form factor and interface that was developed with spinning media in mind. It's time to create a new interface standard specifically designed around the strengths and weaknesses of solid state mass storage.