Before canceling your aion remember they will bump up quest xp in upcoming patch (1.5.1) by as much as 10x from some quests - it should make leveling through questing much more effective / less grindy

About cataclysm, yes maybe it's still 10 months out - that's still too close to be worth grinding to gear up my 80s for me - I will restart wow a few months before cataclysm launches to gather some gold (or earlier if I give up on Aion)