There's no way to upgrade the Solid-State Drive for 2012 Macbook yet. But I assume OWC, the makers of Macbook Solid State Drives, will make one for the 2012 Macbook Air in the near future.
It shouldn't be too hard, as OWC has video and text tutorial for installing SS-Drives.
I recommend upgrading the drive near the end of your Macbook's warranty or after, as changing SSD can void warranty.