I'm not suprised and at the same time, I'm very excited. Lately, there have been lots of rumors surrounding older Dreamcast games, like Sonic Adventure, Crazy Taxi and Jet Set Radio coming to XBLA.
The first thing that came to my mind was "they only have to include something about Shenmue and we can call it a day", I guess SEGA was reading my mind... >.>'...
I don't think it's gonna be as heavy as the original, with today's compression technology can allow to cram the entire game to maybe a full blown GB, maybe 1.5, but not more than 2 GB.
And god forbids me if they actually do it, but they can release it as an episodic adventure game, an episode from each disk, in this case three episodes, or "chapters" a la Fable 2 if they release Shenmue II.