On one hand, the Art of War expansion will bring such radical changes that it will worth a new game. On the other hand I don't think we can jump on it immediately in MP before grasping all the changes by trying the SP. And will take some time too. And I don't want to wait 3 more weeks for the MP.
But the new mechanics could change also the balance in Europe so people might want to chose different countries. I don't think the new provinces will be an issue as in 6 sessions with Crab's internet we're barely starting the colonization.
Sorry, maybe I wasn't clear enough. I'm not talking about provinces that are supposed to be uncolonized, I'm talking about all the newly added provinces automatically becoming uncolonized provinces, because they're not defined as owned in the game (because they don't exist before Art of War). For instance, half of Persia, half of India and so on will become colonizable provinces.