I would absolutely love a Dragonlance book. A new war of the lance, with PCs fighting in great big battles, would be pretty cool.
I'll always hope for a new Manual of the Planes, but there aren't any signs pointing to that next year.
Maybe it is, if these playtest subclasses aren't MtG related, then a Manual of the Planes/Planescape book, but not called that is the most likely book for them.