I like TBC and I would love to see SOD going into TBC.
First of all they should keep adding content that they never added in vanilla first, new dungeons, new areas etc, yes adding new areas etc can make it hard for making SOD going into TBC later if they would add ghostlands etc.
But there is so many possibilities with SOD and if they devs have time and resources to acually do something seriously with SOD, new zones like Mount Hyial, Ghostlands, Uldum etc, new dungeons and no cheap copy like DFC, give us new dungeons/areas, not a copy paste kinda thing.
Seems the karazhan dungeon will be some kind of a heroic dungeon due to its 24 hour lockout, give us more hc dungeons, dont mean you need to make every dungeon a heroic version. Open up CoT with new dungeons where we go back in time.
One CoT dungeon could be when Stormwind falls, eaither playing as a horde when they invade or you play as ally and trying to defend the city. (Whatever the devs think would be the best route to go here and what ideas they could come up with?)
Another dungeon could be Grim batol, not the one from Cata or when it came out, a whole new concept of it.
Make a revamp of ghostlands comepletly, add 1 new raid there and 2 new dungeons, the raid will be the city, then you have ZA there to make something of aswell.
If this is something the devs acually cant do for whatever reason, then it would be better to let us move to TBC imo.