Before you go that far the question is whether or not you really need to. If you got a new one, or even a significant upgrade, what can you do with it that you cannot do now. If you can play every game on high why do you need new cards? Or a new processor? The industry is looking for people to upgrade because they can. Like iPhones or iPads. I always have to laugh at people that stand in line the first day to spend 400+ bucks every year when at best something might have some more memory and a better camera. Oooo... ahhhhh.
My old single GPU is fine for what I need it to do. But I dont play BF4 or other taxing games. However I do need a new one for UDK or UE4 which has more requirements than BF4 ever could have. So there is a definite need there. Otherwise I will save my money and stick with what I've got.