I also agree. I could be wrong here, but implementing a blade SSD design would eliminate the option of upgrading or replacing the drive. So when (and if) the cost per GB for SSDs goes down, you're still stuck with the measly 64 or 128 GB. Pro users, in general, like the ability to upgrade , whereas air users just want the dang thing to work.
The blade-type SSD can be upgraded as easily as a normal 2.5" HD/SSD. It's just help by one screw