But if you're programming on the Mac then it doesn't matter what CPU you're developing for because XCode handles it more or less transparently.
I know. That doesn't make the processor irrelevant. For starters PowerPC is a RISC processor with 32 general purpose registers, the Intel is a CISC chip with only 4. Thus some things will be inherently faster on the PPC, due to it's RISC architecture, Altivec extensions, and ample supply of on-die registers, while other things will be faster on an Intel chip, which has more available clock cycles. Of course they are, and obviously there'll be dual binaries for a high-profile Mac game.
No they aren't they're using CodeWarrior (the cross platform development tool of choice for professionals) and unless CodeWarrior can produce Intel universal binaries, you'll be running WoW on Rosetta for a long time.