I think the past tells us the MBA will be updated alongside the MBP. The last MBP update, on June 2 of last year, we hadn't heard anything about an MBA update when we were hearing/reading lots of rumors of the MBP being updated. Lots of people said/claimed back then the MBA wasn't going to be updated and it's a once in a year (or more) sort of update when it comes to the MBA (like the iPhone). In actuality, the MBA is updated every eight months on average (8 1/2 months for the first update | 7 1/2 months for the second update). The problem with this "average" is there aren't very many past events to "average" out. And it's "ALWAYS" been updated with the MBP (but again those "always" events were only two events). Also the last update didn't provide much of a performance update and instead focused on a price cut to improve sales and try to compete better in a rough economy.
So now we should all believe that there's no reason to doubt the MBA will be updated with the MBP next Tuesday/Wednesday... or as I mentioned in another thread, it sure would be nice if Apple let MacWorld introduce and show off the new MacBook Pros.
I believe that Intel forcing Nvidia out of its partnership with Apple (for post Penryn GPU/chipsets) could complicate the update path and timing of the MBA and other Macs. The MBA will be the biggest challenge for Apple. It could lead to a delayed MBA update, another C2D/Nvidia GPU MBA that focuses on improving RAM and drive space, an MBA with only Arrandale's IGP, or an MBA that has a dedicated graphics solution (or hybrid using both the IGP and dedicated solution automatically switching graphics depending on the load demands).
I will gladly prefer waiting for an MBA update that includes a dedicated ATI graphics system with 512MB of RAM. I don't want Apple to "rush" this decision and for us to end up with a repeat of the disastrous original MBA. Therefore, not seeing an update to the MBA, when the MBP is updated, is probably in the best interest of us future MBA buyers.