I saw this on imdb.com, is this going to be an Xbox game, like the one out now, or will it be for all three systems, or PS2?

I think I read it will be on X-box and PS2. It's not from the same company though...

Actually I think it is all three unless they cancelled the GC version.

Sierra is the new publisher and last I heard it would be on all three consoles.

Any mention whether there will be any differences between the versions game-wise?

I think they have a bunch of different multiplayer types and no word as of yet, that I know of, if they licensed the game engine from the original from EA or what engine they are using. Let's hope they don't screw it up.

I hope it's only PS2 or GC because I don't have an X-Box and I'd like to play a Buffy game

It's all three. If you really want to play it, pick up an xbox and get the original. Easily one of the best games on xbox.