Toms Hardware writes that Apple will transition both the MacBook and MacBook Pro to Intel's new Westmere platform later this year.
It is highly probable that Apple will base new MacBook and MacBook Por units on 32nm Arrandale Core i7's. With 2 cores and able to process 4 threads, the new MacBook models will be able to save even more power, thanks to the smaller fabrication process as well as optimized processor features.
Intel is expected to ship the Arrandale Core i7's in Q4 of 2009. It's like that Apple would do a minor refresh before that time.