It's hard to ever say for certain precisely when one is "done" with an MMO expansion, but this is pretty much the end of the line for my mage. Earlier this week, I hit exalted with the Frostborn Dwarves, the last 5-man dungeon faction I had yet to complete. Over on the Horde side, there are a few more reputations I could complete for heirloom head and shoulder enchants, and maybe a few more Heroic 5-man dungeons to complete once for the respective achievements, but nothing I'd cry over missing.
I suppose the interesting commentary here is that all the things I am still working on are non-RNG based goals. Theoretically, I could keep farming the elemental invasion bosses for a few upgrades, but these will all be moot in about a month anyway. I've actually had some pretty good luck with the random number generator this expansion, but I'm just not as interested in rolling the dice this close to the end of the line. At this stage in the game, it makes much more sense to focus on finishing off things I was already working on, especially if they offer something that will stay with me into next expansion, such as a title or heirloom.
I suppose that the long term question, after an expansion cycle that featured frequent and dramatic gear resets, is whether the picture will actually look that much different in a month.