Well you know, when you start a horde character now you have Garrosh as the warchief and then you get to outland and suddenly Garrosh isn't warchief anymore, does that make sense? No, did they care? No.
The same way they phased Krarasang and are phasing North Barrens, they can easily phase Garrosh out of Org. They already phase Anduin out of Stormwind.
---------- Post added 2013-04-03 at 10:33 PM ----------
I can't imagine a situation that would leave Garrosh in power and have Vol'jin stay leader of the trolls that doesn't involve the trolls no longer being members of the Horde, so my money is still on Garrosh being replaced.
In any case, the problem is that from one moment to the next there is a different warchief, and that can be confusing to players, especially newer players. You can say that the raid explains that, but chances to do the raid over LFR after MoP are slim.
IF I was Blizzard, I would do the same way as Anduin and at lvl 90 / moment we pick the new xpac quest / whatever, Garrosh phases out.
Garrosh is so out the door as Warchief. I cant see any way that he could possibly be allowed by the Horde to stay. Once your own side turns on you, you are toast.
"I hated hating Garrosh before it was cool."
FOR THE HORDE!!!