From what the rumors tell me, the 700 series are going to be rebranded 600 series cards, shifted one up (ie. 760TI = 670, 770 = 680). By they're just rumors. AMD has (had?) a Never Settle Bundle, where they bundle some games (FC3 Blood Dragon, Bioshock Infinite, something like that) along with your graphics card, so if you planned on buying those, you're essentially saving yourself some money. Personally, I always go with NVIDIA, as Inspector is too useful of a tool to live without.
EDIT: Unless you're running multiple displays, a really high resolution, or 8X SGSSAA, you don't need 4GB of VRAM. Get a 2GB 680 or the 7970.