They don't have a Levitate spell to work from presently, so they need to develop that. However, I don't think we can really move vertically straight up in the game engine. At least, I can't think of any creatures/effects that use/produce this type of movement. But, in the end, I think this is just an engine limitation that they're not willing to spend the resources to alleviate.
It's a shame really, flying would be super cool, if not super intelligent, thing to do given the concentration requirement.
