This is obviously not a leak or otherwise relevant information to the next expansion, but a personal wishlist:
1) Backward Application of Levelless Content. It would make things so staggeringly fantastic if players could do any old world zone from start to finish without outleveling it, but it would also be wonderful to do ANY old world zone from start to finish regardless of level. I'd still suggest gating BC/LK/MoP/etc to their minimum levels, and have all Raids and Dungeons have a minimum level (So you've got a certain number of abilities to use in said dungeons appropriate to their difficulty), but with no cap-level, it would make it a ton of fun to be able to "Timewalk" without waiting for Timewalking week.
2) Actual Ships to function similarly to the Vindicaar. Throw some NPCs onto it, make it a Racial ship, and have it be our way of traversing the different islands of the next expansion... but also give it the ability to travel to ALL OTHER REGIONS. Let us hop onto our boats in Stormwind or Orgrimmar and use them as a fast travel method to all other locations with ports. Wanna head to Northrend? BOAT. Wanna go over to Tanaris? BOAT. It would give us a lot of personal freedom without being overbearing, I think. Make it our "Order Hall" with different followers as different positions on the crew. Have us send our ship out on missions, locking us into a location, more or less, for the half hour 'til it gets back or whatever (No multiple day order missions, obviously!) And between this one and the one above, it makes 3 tenable.
3) Use World Quest Tech to give temporary makeovers to old zones rather than focusing all of the content on a new continent. Rather than putting all of the content on the South Seas islands, give us quests across Azeroth where we have to deal with the Twilight's Hammer or Old God Corruption or the Scourge or whatever the threat is, -everywhere-. I'd love to go back to Icecrown and fight against a new Scourge Army driven mad by Yogg Saron. To race across Pandaria fighting the minions of Y'shaarj. To delve the deserts of Silithus and Uldum and face C'thun's forces in battle. And yes, to head back down into Vash'jr to fight against N'zoth's machinations in the Abyssal Depths. The game is called WORLD of Warcraft. Not New Continent of Warcraft.
4) The Rising Tides of Azshara. I wanna play a Naga. I know there are technical limitations, but that's okay. Gimme. And gimme that South Seas expansion where she's stolen the Tidestone of Golganneth to try and further empower N'Zoth after the stabbing of Azeroth using Titanblood to reforge it into it's original whole, rather than the broken version we have in the wake of the destruction of Farondis. Have her be the big Tier 1 Baddie we've got to deal with in this new front of the battle for Azeroth, but not the only one...
5) The Return of the Lich King. Bolvar driven mad by Yogg Saron and Ner'zhul, brings the Scourge to bear. During the first part of the expansion he'd mobilized them against the Twilight Hammer and helped us fight using undead hordes with Greymane endlessly worrying about Sylvanas taking on his power or seducing Bolvar or something. But in phase 2, the madness of Yogg Saron drives him, tricks him, into going after -all- of the peoples of Azeroth. They're all infected with the Curse of Flesh, after all... They're ALL corrupted by the Void!!! So we get a miniature Wrath tied into the Azsharan uprising. Azshara gets away 'cause she's slippery.
6) Old God Mobilization. With The Lich King and Azshara both still in play, we wind up having to re-cage Y'shaarj, C'thun, and N'Zoth. Putting N'Zoth away as the final step of the expansion raid-end, with world quests of Scourge uprisings and the like still going on leading into the next expansion's full on Lich King revival. In which we must re-cage Yogg Saron, restore Bolvar to Sanity, and thus contain the Scourge on our way up toward fighting in the Void.
I didn't wanna put this into the Speculation thread, 'cause it's not -actually- speculation, but it is kind of what I'd love to see.