If Apple can find some way of wirelessly connecting to a CPU and GPU then more power to them, but OSX on ARM is not going to cut it as a replacement computer for people who need a computer. And that's the point of a hybrid.
Well, the base station could be Intel, and somehow sync all user settings with iOS on the iPad. But ARM could also work for many people, as long as new apps are written to run on it that do the tasks currently done on Intel systems. I know the recent "upgrade" of iWork is very unpopular because so many features went missing, but going forward, iWork on iOS is supposed to have feature parity with iWork on OS X. From there, it's not that big of a step to have a version of OS X compiled for ARM, and have an iWork and iLife suite that runs on that, and is compatible with iWork / iLife for iOS. And for many people, that's all they need a computer to do.