Too small of an upgrade, if you ask me. http://www.techpowerup.com/reviews/ASUS/GTX_650_Ti_Boost_Direct_Cu_II/26.html
performance wise, the difference is kinda small.
Also Battlefield 4 is possibly going to be an AMD favored game, as the demo of Battlefield 4 ran on a Radeon 7990 reference GPU.
As it is right now, no one is sure of the requirements, so better hold your money back, because the upgrade will not get you far.