Probably because the next gen consoles will be very similar to current gen PCs. The next Xbox will likely be running DX11 (like current PCs), unless Microsoft suddenly comes out with DX12. And DX12 would likely be compatible with DX10.1 and later. Other than that, the next gen is likely going to consist of little more than faster chip sets and more cores. All of which current PCs have over the current consoles. So really, it's not that hard.
