So you're telling me that the CPU caused speed improvements you notice each time you Aperture, iMovie or other Apple apps are less relevant than the GPU losses some people are expecting (they have not been benchmarked anywhere yet and might only be visible when gaming)? Let's agree to disagree on that.
As for the timing: I know Apple is moving towards a yearly schedule, but a shiny new MBA might be a nice item to use when presenting the final version of OSX 10.7, don't you think? If you add the argument that buyers might not want to keep buying a four year old CPU and 64GB SSDs until late 2011, it's possible that we'll see a refresh before summer.