I'll bet $5 that the MacBook Air in the future (18-24 months) will switch to ARM once the >2GHz ARM processors start shipping en masse.
The Asus Eee PCs running Android with Snapdragon processors already embed the Cortex-A9 MPCores.
ARMS's Achilles' heel is that it's only 32-bit, and I don't think anyone wants to go back to a segmented address space any time soon.
(seriously, I'm not trying to troll. I've had exactly one - making sure a project of mine would compile as PIC and that was pretty minor after the required reading)
I expect ARM's transition to be quite different though--with the highest ends of their business moving in only a couple product cycles, and the lower ends of their business sticking with 32 bit indefinitely.
By extension, if they are satisfied with 32-bit programs and don't feel a need to switch, then they won't miss 64-bit architectures.
Virtually all of the computer users that I know limit their use to an office application and a web browser on top of Windows. That's it. The web browser gives them everything they really need. I wonder how many computer owners could even tell you if they have 32-bit or 64-bit or how the two differ. Probably the same percentage that can tell you detailed specs about their car engines. Virtually none.
The only computer specs that matter anymore --exempting programmers-- are weight and battery life. A few hardcore gamers still care, but they're in the minority, even for video gamers. XBox anyone?
And when they converted to Intel, they also provided Rosetta, a completely ridiculous binary translation system to make PPC apps work.
Those are bad examples.
Hope you're still around in 2 years; it can be interesting to ponder a falsified prediction and wonder, why did I believe that?