kookie3010 :
Last i remember playing bf3 i was using 1.7gb of vram.Bf4 might go over 2gb.still just turn aa of or low if it does exceed the 2gb limit on your card.if you are still unsure return your card and get the 4gb.since the game is not out yet,there is no way to test it on a 2gb card/4gb card.
Just because a card shows X amount of vram usage does not mean it needs that amount of vram to run at 100% normal performance.
Example: http://www.bf4blog.com/battlefield-4-alpha-gpu-and-cpu-benchmarks/
You'll see it shows the game uses more than 2Gb of vram, yet the 690 beats the 7990 soundly, and the other 2Gb cards have the same minimum and averages as their 3Gb counterparts. Even at 1600p.
Memory management can be more lax when there is extra vram, so it will show more vram used, but that is not to say it is needed. In this case it is not.