As of Sunday night, all 2010 model MacBook Airs have become unavailable for shipping on Best Buy's site, sometimes an indication of an imminent Apple model update, according to Mac enthusiast site 9to5Mac.
Indeed, a quick peek at the Best Buy site shows the models that were refreshed in October of last year--four models in all--are "not available for shipping". (The only MBA that is listed as available is, oddly enough, an old model announced way back in October of 2008. So, it is not in line to be updated anyway.)
Low stock of multiple models is "usually indicative of a product refresh...Additionally, a number of stores have indicated to us that they are exceptionally low on MacBook Air stock," wrote 9to5Mac.
Most reports and indicators point toward a July update from Apple, along with OS X Lion. That said, there are still a few days left in June. We won't know for sure until the MBAs pop up on Apple's online store. Go ahead, hold your breath, if you can.