Apple's tricky decision to go with C2D in the Airs still looks sensible. It's all about Ivy Bridge and the ULV Sandy Bridges due at the end of the year.
The big question is what exactly does the rumoured settlement between NVIDIA and Intel look like?
If the dual-core versions put out similar numbers and run OpenCL code decently, I think we can safely predict that Apple will go back to Intel integrated graphics with no discrete GPU for the 13" MacBook Pro and the MacBook Air line. A significant CPU boost and no appreciable difference to the 320M on graphics performance should lead to a nice upgrade.