GTX 680 isn't next gen. It is definitely on track. The follow on to it, Maxwell, in SLI format, would probably fit the bill. Any customizations that Microsoft requests on top of it the icing alongside DirectX type advances. In other words, you need to be able to run something better than the Unreal 4 engine without SLI, and at least 100 fps, ideally 150-200 fps, so you can have a little leeway for 3d application at 120 fps. It's getting close. I'll give you an example. The GTX 680 is the equivalent to the Nvidia 6800 series. Still had to wait until the 8800-9800 series to make a plausible 360/ps3. The next jump by NVIDIA is supposed to be even bigger, based on their DP GFLOPS per watt Basically a console version of Nvidia's Maxwell (1st or 2nd version to be determined). http://techreport.com/discussions.x/19675 "The Maxwell architecture will come next, in 2013, and will be produced on a 22-nm fabrication process. Maxwell promises nearly an 8X increase in DP FLOPS per watt beyond today's Fermi chips. Huang noted that, in parallel computing, power is the primary constraint, which is why he chose that metric to describe future architectures."
