Yeah, I think console gamers simply will not accept a full price online-only FPS. For that price, they expect a single-player campaign as well. And I pretty much agree with them.
Back when PC FPS games went from having long single player campaigns plus multiplayer(Duke Nukem, Quake, Unreal)to multiplayer only for the same price (Quake 3, Unreal Tournament) I thought it was a rip off. The Battlefield series was the only exception where the multiplayer content seemed so extensive that it justified the cost. But I doubt I'd feel that way if I was playing on an xbox with smaller maps, fewer players, and a monthly online fee.
Or for a more recent example, look at the failure of Unreal Tournament 3 on consoles compared to the success of Gears of War. Certainly the lack of a true single player component in the former had a lot to do with that.