But since the introduction of Zul'Gurub, we haven't seen any other options for mages in game. And there are plenty to choose from by now-- Polymorph: Ravager, Polymorph: Clefthoof, or Polymorph: Elekk would all work great. Polymorph: Willy would even be lots of fun. Oh, and yes, as players in the thread say, since we're headed to Northrend, Polymorph: Penguin would not be out of order in the next expansion.
Blizzard has done a pretty good job of taking mounts, both flying and ground-based, towards a little horizontal progress-- giving more options on one level instead of setting up a few options over multiple levels. But hopefully Polymorph will get a little love, too-- even though mages are the only ones who benefit directly, my guild has always had fun making sure our mages have all the Polymorph options possible.