Apple is planning to refresh its MacBook Air lineup with new Intel Sandy Bridge processors sometime in June.
According to CNET, the MacBook Pro series is also in for an update. It's worth noting that Intel has relied on Core 2 Duo parts for the Air since its introduction in 2008. Basically it skipped an entire generation of Intel CPUs.
This will probably mark the end of the line for quite a few entry-level Nvidia GPUs used in Apple notebooks. However, the new processors should be quite an improvement over the ageing C2D generation, as they consume quite a bit less power and offer superior performance, particularly with Turbo.
The fact that Apple has hardly changed the original design of the ultrathin Air is a testament to its design prowess.