Luckily that turned out not to be the case and the third-generation Air ships with its SSD on a blade that's socketed to the logic board. Translation: you'll be able to upgrade to a higher-capacity SSD.
The blade SSD was confirmed today when iFixIt performed a teardown of the MacBook Air Mid-2011, noting:
Apple is continuing to use a modular design for the MacBook Air's solid-state storage, meaning that it can be replaced or upgraded if necessary, although it is not officially supported as a user-replaceable component by Apple. A report in the weeks leading up to the machine's debut had claimed that Apple might be shifting to new Toggle DDR 2.0 flash memory, which would be soldered directly onto the motherboard. This is not the case, however, with Apple continuing to use a separate, pluggable board for the solid-state drive.
Granted, SSD upgrades for the MacBook Air aren't cheap (OWC's 320GB model costs $779 and its 480GB SSD fetches $1,399) but if you need the extra space, it's nice to have options. A socketed SSD is important for anyone considering moving from a traditional hard drive to a SSD as they give you the option of having hard drive-like storage capacities in a zippy SSD -- albeit, for a price.
Unfortunately, the RAM in the MacBook Air (Mid-2011) is still soldered to the mobo leaving no upgrade path from the 2GB or 4GB that comes standard.