PC/Console convergence? Eventually leading to a "build your own Xbox, or buy one of ours" in a shared ecosystem.I can't see any reason why MS would make a gaming mode, they've already got an OS with a gaming mode, it's on a device called an Xbox.
A desktop doesn't really need a gaming mode IMO and I can't see how it would result in any substantial performance improvement.
Battery life improvements are always welcome though, even Apple can't get that right with the new Macbook Pro.