What is the resolution you want to play BF4 with? If you're not going over 1080p or intend to do 3D, there's no need to go any further than a 7970(standard or Ghz edition). BF4 will be one of the first games to feature Mantle API support, which could potentially be a big performance boost for Mantle compatible cards such as the 7970.
Mantle is an open platform so Nvidia can jump in later down the road as well, but as of right now there has been no word from Nvidia regarding Mantle. BF4 will be getting Mantle support this December.