I'm not so sure, and the reason I think this is because of the texture sizes considering the new graphics engine. Otherwise they'd have to put all the textures on the second disc which could take up alot of space.
It really depends on how they go about it. If they do multiplayer and campaign seperate like Halo then probably not (though I wouldn't rule out the possibility). If they go the Forza route then yes. Forza route would be better in my opinion.
All we currently know is it's on two discs until further information is revealed.