Just imagine the current "touch" object with additional mouse related events/vars.
If I create a game today with the touch object I can convert it to the mouse in no time - simply check the "simulate cursor". This, to me, should be expanded till there's no separation between mouse and touch objects. Just 1 expended object - Touse or Mouch, which will cover all events/vars.
I totally agree about the multi-touch. This is a special case and as far as I recall the touch object itself doesn't deal with that. The behavior "Drag and Drop" does this well but the touch, AFAK, doesn't deal with "Touch" for example.
As I see it, people will keep creating games in the mouse environment while testing them on touch environment. In such operation it's best to develop on the "touch" object and check the mouse simulation. If the touch object will be expanded it will cover both mouse and touch games.