...Since Trassk is one of the few people who isn't constantly using bad English/grammar I can actually read his posts.
Having said that, what little we know about the next expansion (whose name I assume will be announced at BlizzCon) is Alleria and Turalyon will return or at the very least be directly referenced. What Varian didn't say to Alliance Players after Garrosh is downed is what I find the most telling:
He took the other Horde capitals (TB, Echo Isle and Azshara) on Kalimdor off the table even though it's pretty obvious the Horde wouldn't have been able to put up much resistence after having thrown everything at removing Garrosh from power. Wrathion's reaction to Varian's decison to not escalate hostilities right then and there confirms Varian wanted to avoid a repeat of what Lordaron did with the Orcs after the Second War. Having been used as a Gladiator himself I don't see him as the kind of guy to do that to the Horde even though no one would blame him if he did.
Now, going back to the New Warchief, Gilneas and The Undercity/Lordaron:
If not for Godfrey's Treachery The Forsaken would've taken Gilneas. The Forsaken withdrew so Sylvanas could recover and to deal with Godfrey directly (I prefer to believe the Horde version of SFK is canon since the assassination attempt is more personal for the Horde than Bloodfang settling the score). After dealing with him The Forsaken shifted their focus to expanding their territory into the Former Plaguelands. Sylvanas was explicitly banned from using The New Plague (which didn't stop her from using it in Gilneas and Hillsbrad) so she used her other trump card--the Val'kyr--to win Andorhal for the Horde.
I doubt Darion Mograine and the Argent Crusade will stay neutral much longer, either. The Crusade has been busy mopping up what's left of the Scarlet Crusade and the Cult of the Damned/Scourge while the Ebon Blade would likely consider Kolitra a hostage and not an enemy combatant. Varian said the next move is containing the Forsaken (which you can be sure will make Genn a very happy Worgen King). He said contain, not defeat which means he at least knows Sylvanas has Val'kyr under her control.
Since Lordaeron and Gilneas will likely be the next big battlegrounds in the Alliance/Horde Conflict I'm expecting Genn to take point with support from the Night Elves and maybe the Wildhammer Dwarves (Aerie Peak is nearby). Stormwind would play a support role since the Gilneans know the area best. Sylvanas would take point for the Horde obviously with support from Silvermoon and maybe the Revantusk Tribe. Since Vol'Jin is the new Warchief he's kinda forced to stay in Durotar until things get organized though he'll definitely be involved somehow.
Thus, Genn v. Sylvanas Round 2 will soon begin.
As for how Vol'Jin as Warchief effects the Horde, I don't expect any objections from the other member races except maybe The Forsaken and the Orcs who sided with Garrosh (most of whom were wiped out during the Seige of Orgrimmar). Thrall is the "new" Warchief of the Orcs. Much doesn't need to be said in that regard in terms of his qualifications. He's probably the only one capable of rallying the Orcs post-Garrosh around the new Warchief, who for the first time is not an Orc himself. Thrall has his work cut out for him convincing the young and impressionable orcs who treated Garrosh like a rock star his way was not only wrong but the Orcs are better than that.
No different from when Thrall first became Warchief when you think about it.