Remaking Halo 2 is a waste. It was a garbage campaign and totally broken multiplayer with some decent maps. At least Halo 3's campaign was fun to play through...
CEA should be the only remake, and that's it. No more.
Now, if they wanted to totally remake Halo 2 (i.e. do more than just skin over it) that would be a welcome addition. Make the levels not so ridiculously linear, make the Earth missions much longer, get rid of 1SK jackals, make the Arbiter missions not so painfully boring, etc.
In a perfect world, I would ask for a total remake of the trilogy + ODST for the next generation Xbox. Won't happen, shouldn't happen.