They did, but the Pointer API is a browser API, not an OS API (supposedly anyway, since they proposed it for W3C standardization), and one of its purported advantages over the current standard (Apple's touch events) is that they're "pointer-agnostic" so instead of having mouse events, touch events, and some sort of hack to back-support mouse events on touch devices, it's all supposed to mostly work on all devices.
So they should be able to implement their API on win7, since they're suggesting others can (and should) do it on pretty much every OS out there.