While I don't think Thrall should become Warchief again, saying he should be exiled is just silly. While the Alliance SHOULD demand something and get something out of this other than killing Garrosh and handing Orgrimmar back to the Horde, it would just be silly to have them demand Thrall's exile, especially considering what he's done in Cata. Saving the world outweighs putting a bad orc in charge of the Horde.
More realistic demands could include having Forsaken pull out of Gilneas, horde forces pulling out of Ashenvale and staying out, handing over Thelon Songweaver etc. I could even see the Alliance demand Sylvannas' head on a platter though they'd never get it. But I see no reason for them to demand thrall be exiled.