Of course, Mists of Pandaria is a long time away. We've got an entire content patch to get through first. Bashiok hit the forums today to explain why the talent calculator is available so early.
He points out that these talent trees are definitely going to change; we're still in a pre-alpha stage of development. Since many of those changes will happen in response to player feedback, getting the dialog started early is a good thing. More importantly, the hope is that by revealing the early talents, players can get a better idea of the design philosophy behind changes.
Whether you dig those reasons or not, we're all clearly very excited to get our hands on the talents. Check out what Bashiok said behind the cut.