Chose some rather random choices in the fortune test and got druid , which is one of my lesser played of my 80s =\. We'll i guess shaman and druid are closer to me personally than what i actually play (a deathknight).
It doesn't make sense either way, we've had flying mounts since BC and now suddenly we learn to fly them in Azeroth? Dunno why the world changing has anything to do with us learning to fly. It's one of the selling points of Cataclysm, like archaeology.
So would be the new class combinations but they are offering that to us now. They could have also offered to us flying.