Intel has said the mobile CPUs are not upgradeable. Buying one would be a waste of money. The performance bump for Ivy Bridge is very modest and probably not worth the trouble. The GPU is where Ivy Bridge shines and that's not upgradeable at all.
Eh? The GPU comes with the processor so if you replace a Sandy Bridge with an Ivy Bridge, you upgrade the GPU from HD3000 to HD4000 (my main reason to upgrade). Now, that this is actually possible (the missing software part mostly), I'm not sure.
And yes, I agree, I wouldn't burn my money trying right now as it just came out. But later down the road be sure that I will. And by the way, since my only interest is the GPU, I'd rather pick a lower end model. Though it seems that i7 models have faster GPU (a few extra MHz in turbo)...
I know for a fact, though, that in the Core 2 Duo days a Penryn CPU could be dropped in any Merom motherboard. It displayed an error but it worked. I wouldn't be surprised if it's the same with Ivy Bridge.