I think cross chat will be available through both platforms. I can see re-downloading all XBLA and Indie game titles on the 720 but whether they charge a fee for doing such? I'm not sure.
Years of Gold/MS points will stay the same.
I don't see them dropping the cost of XBox Live because so many people are currently paying or it. I can see more deals, say maybe $40 a year but in general the price will stay at $60 a year.
It's just that simple.