With Apple's tradition of jumping onto the latest bandwagon at the start of a major product transition, such as chipset or CPU, we're expecting a transition to Intel's new Westmere platform later in the year.
With the recent release of the unibody MacBook and MacBook Pros, Apple continued to base its notebook line on the successful--and still powerful--Core 2 line of processors. At no fault to itself, Apple couldn't really move to a Core i7 platform on the recent release due to the fact that Intel didn't have a true mobile Core i7 processor. However, Intel will have a very powerful offering come Q4 of 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.
Like the new MacBook Pros, the new ones will also feature integrated graphics as well as a discrete graphics option. For the ultimate in power savings, users will be able to utilize the iGFX solution that's integrated into Arrandale. For performance moade, Arrandale supports switching to a discrete GPU, but expect to lose a bit of battery life.
We're expecting Apple to announce new MacBook and MacBook Pros later this year.