There will be more bases, but not too many. The basic idea is to group them. So Fire will also stand for heat, burning, etc. while Water will also stand for ice and thus cold. Aside from the elements, there will be bases like Death (for all those necromancers out there), Body (for healing and direct-damage) and Mind (for all those control and influence spells). I can think of a few more, but once again, please post ideas you have below.
Aether, for things like teleporting & making things invisible.
Entropy, for shape shifting and various chaotic effects (not quite sure what can be said to be "chaotic" but I'm sure someone can think of a use).
Nature, growing / controlling plants & trees
