I certainly hope that you are right about this because it would mean the announcement of a new MBA would be made either two or three weeks from next Tuesday. That's not very long.I actually think the [MBA] update will come one of the two Tuesdays before WWDC. I believe Apple has enough to introduce at the WWDC, so it should update MBA before WWDC, unless the MBA gets introduced as the "one more thing" at WWDC as a completely new MBA then I guess I would be completely wrong about the CPU/GPU used in the new MBA.
I would love for the announcement be another of those where Steve Jobs says, "Oh, and one more thing," and procedes to blow our socks off. Unfortunately, I suspect that your prediction of a pretty modest upgrade is the more likely outcome.