Can't the 360 support a USB Mouse and Keyboard? I'd be very surprised if it doesn't, and if it does then this game will surely have mouse and keyboard support.

I can see this going either very well or very badly. An RTS would fit the Halo universe perfectly, but it could well end up being an average game made to capitalise on an awesome licence. I sincerely hope that won't be the case, though, and I'll be following this game with interest.