It doesn't make any sense to "hold back" hardware for an OS update, when there is no stock in the stores and customer demand. Can you imagine if you went to a car dealership to buy a car, and 10 others were waiting to buy a car and they said "sorry, we're out of cars for the next 3 weeks because the new models are going to have a new feature" ... that's absurd, and that's not how marketing has ever or ever will worked.
There has been ZERO credible info to support any correlation between when the laptops would be released, and when Lion would be released. There has never been a case where they altered hardware (look at Leopard - drop in disks, look at Snow Leopard - drop in disks) release plans for a OS. IF they were going to do a big day where they refreshed MacBooks, Macbook Air, Macbook Pro, and Mac Mini to coincide with a Lion release, do you not think APPLE of all companies would hold a media event to hype them up? Of course they would.
I know we all WANT to see new MacBook Air, and maybe it'll happen, but the odds are that it won't until the fall. Why would they refresh the MacBook Air when stores are still selling large amounts of the existing model? Look back through the old threads, there were dozens of posts just like this one swearing they were going to update the MBA (1st gen) every other month practically, and it took them a year and a half. Just because you WANT something, doesn't mean it's going to be reality.