I'm pretty much in the same situation now, and unless something changes, I don't see myself resubbing.
I think that at this point, Blizzard needs (besides getting their **** together, obviously
) to add random-based stuff around the world (including the old world). Quests that spawn in the wild with no fixed place and with random objectives. You can already pop a quest giver in a random place, so I don't think the technical hurdle is that huge.
Adding random spawns all over the world (again, with no fixed spawn points, or at least a path taking them through an entire zone). Obviously, rewards would have to be high enough to actually bother doing that, but it's doable. Not to mention adding random events in old world (maybe a start of a Burning legion invasion, or groups of Iron Horde that somehow get portalled to Azeroth). Randomized stuff like that goes a long way, because it's, well, randomized.