I feel like Tandred Proudmoore, brother of Jaina, will play a major role in Mists of Pandaria.
First off, Theramore will be destroyed and of course Jaina could be killed. This brings Kul Tiras into the picture; Theramore is autonomous from but strongly allied with Kul Tiras. Both are naval strongholds of the Alliance. It makes perfect sense for Tandred to lead the naval fleet of Kul Tiras, the Alliance's most powerful, to war with the Horde. Upon early arrival in Pandaria, he could also likely be the leader of the Alliance forces on the island. I always think of Mists of Pandaria as something similar to the historical Scramble for Africa; Tandred could fit that role as a leader of such a push for control and resources.
He is the Lord Admiral of the Kul Tiras navy, for those who might not be aware.
That man in the tattered naval uniform that you saw in the Mists of Pandaria artwork?