Update: Both EA and AMD have issued statements on the exclusivity, and it appears it isn't actually exclusive. The two companies are collaborating on day-one support for Battlefield 4, but it's a non-exclusive partnership so products from NVIDIA will be supported.
EA issued the following statement:
DICE has a partnership with AMD specifically for Battlefield 4 on PC to showcase and optimize the game for AMD hardware. This does not exclude DICE from working with other partners to ensure players have a great experience across a wide set of PCs for all their titles.
While AMD issued this statement:
It makes sense that game developers would focus on AMD hardware with AMD hardware being the backbone of the next console generation. At this time, though, our relationship with DICE and EA is exclusively focused on Battlefield 4 and its performance optimizations for AMD CPUs, GPUs and APUs. Additionally, the AMD Gaming Evolved program undertakes no efforts to prevent our competition from optimizing for games before their release.
So there you have it. AMD and EA are working together to better optimize Battlefield 4, but it isn't an exclusive thing. NVIDIA can still work on its graphics drivers on its own, just it sounds like it'll be relying on NVIDIA engineers only.
In a rather stunning turn of events, EA has announced a partnership with AMD where all Frostbite 3 games ship optimized for Radeon graphics cards and AMD CPUs. Starting with Battlefield 4, all upcoming Frostbite 3 games get an exclusive optimization to perform the best on AMD hardware as soon as the game launches. NVIDIA, meanwhile, will have to wait until the Frostbite 3-powered games are available before it can work on driver optimizations.
It's a very bold move, but one that potentially shows a tipping of the scales in AMD's favor. Tomb Raider, Crysis 3, and others have received AMD optimizations, while NVIDIA has had to wait until the game is readily available. NVIDIA's performance in Tomb Raider was especially bad, which prompted the company to launch a beta driver tuned just for the game.
Given AMD's hold on the next-gen console market, and now EA Frostbite 3 games, it'll be interesting to see if there's any kind of a counter from NVIDIA. However, based on NVIDIA's E3 press conference, it doesn't sound too concerned with the next-gen consoles. The company is dedicated to PC gaming, and considering the large amount of games shown during its E3 press conference, it doesn't sound like NVIDIA has much to worry about. Still, the inability to have NVIDIA day-one drivers for Frostbite 3 games is something to keep an eye on.