No matter what processor they might have moved to, emulation would've been necessary, but I'm sure it would've been implemented transparently like Apple, and like AmigaOS 4 and MorphOS. You can run a 68k executable, and usually it's tricky to tell that it's a 68k program at all. The PPC was supposed to be well suited to 68k emulation though, and with Motorola promoting it as such, it's difficult to see what other chip they would've given serious thought to.
