The next MacBook Air may have a speed boost by incorporating the Penryn processor. Here it is from PhoneNews:

In fact, the new revision of the MacBook Air will draw it much more in-line with the current MacBook internals. Expect to see SSD prices in-line with the current revision, however the hard drive version of the MacBook Air will likely be upgraded to 120 GB, and optionally 160 GB, due to falling prices for 1.8-inch hard drives.