I'm not much of an online player, but if they could have that portion of the game ready, it may stand a good chance.
I see many players on XBOX, like to set lap times on leaderboards. Setting a hot lap in a Mk1 Escort around Mount Panorama, then seeing where a player is ranked, is a big thing.
Another thing is, PCars has the physics and AI basics, car and track diversity. Heck, I'm not even wanting for a livery editor in this game. However, what else is there to make this a worthwhile purchase? Online playability. For the XBOX community, it's a must.