My guess is they're going to have Thrall and the others interact with several different characters in the SL. Cairne in Ardenweald for Baine & Thrall. Kael'thas in Revendreth for Jaina. Uther in Bastion for Jaina. Draka in Maldraxxus for Thrall Garrosh in Revendreth for everyone
Though I'm definitely leaning on a more personal interaction between Thrall and Garrosh. They've just got a lot of beef that could help each other out in their current situations. We know Thrall just unlocked his Shamanism block recently but maybe it can be tapped into further.