It's a wrong assumption, the difference between x86 and PowerPC is a hurdle for porting. These days it does not involve much mpre than a recompile, the same compilers are available for all major CPUs. Think for a moment about cross-buy. It means porting between PS3 and Vita is so inexpensive, that it is enough to buy one of the games. The difference between PS3 and Vita is a lot more than the CPU.
The reason why 3rd-parties don't release multiplats for WiiU isn't that is as a different CPU. More of an impact is, that the WiiU is less powerful. But most importantly games sell bad on WiiU.
As compilers are readily available for all major CPU-architectures, the only consideration is, if the CPUs can be produced:
a) reliable
b) cheap
c) in big amounts
PowerPC, x86 and ARM are currently fitting that.







