Right now, the new GSL only includes the 8 original character classes, so there could only be 8 class splatbooks. Should there be a GSL revision in the future, we'd be certainly interested in writing a Quintessential Sword Mage... we'll see.
You'll just have to wait a few months for that... ;)
Hi, this is Marco Picone from Asterion Press. In the new Quintessential line, we've tried to stick to the D&D 4E unwritten rules about feats. They have been revised several times before printing, to ensure they weren't too powerful and "must have". I hope you'll like the result!
As one of the authors and the project manager for the new Quintessential line, believe me when I say that everything has been either fully converted to 4E or (most of the time) created from scratch.
While we're trying to take all the best ideas from the 3E Quintessentials, D&D 4E just requires...