If you find the chart with 1680x1050 at Low preset you'll see that your setup gets 50fps. Now, if you dropped down to 1366x768 at Low...I'd guess 65fps. So, you could go to Medium and get around 45-50fps. (guess)
So, I'd say BF4 on Medium with 30fps. (mind you it's a guess cuz game isn't out yet but you can guess it will be more GPU intensive) Your setup is ok, but I'd wait until you try the game out then decide if you want to upgrade your GPU.
If possible I'd suggest upgrading the GPU. It'll play the game but not as well as you might like.
A note, as soon as BF4 comes out all the BF3 servers are going to start disappearing. Also, you'll be playing against people that have all the guns while you're a noob running around with a pistol. Just wait for BF4 and play that instead. Should be awesome.