Honestly, I'm not sure where this belief that only a CPU upgrade is worthy of being termed an update,
Since the Intel transition, there have been no updates that have not involved some sort of CPU bump (if I've missed any let me know). Furthermore, there have only been a few updates that involve only bumps in the existing CPU range (not, say, Merom to Penryn or Q1 2009 Penryn to Q2 2009 Penryn). The MacBook Air is using both Penryn LV CPUs right now, so such a bump is unlikely.
and that Apple's marketing is immovably welded to Intel's roadmap, came from.
There aren't many updates that don't follow Intel's schedule. Besides the Mac mini (which is far behind anyway), the Mid 2007 MacBooks and 2008 iMacs (and 2007/2009 Mac Pros in a way) are the ones I can think of.
It's a bit ridiculous to be honest. There's plenty of stuff they could improve on the MBA without much perspiration.
It's true that the CPU isn't the only component that can be updated, and isn't the main component that can be updated either (I was saying something like this before the MacBook Pro updates). But most of the time, update dates revolve around CPU update dates, and that is why I'm saying H1 2010 for the next update.