Possible. If it is only 6 hours, then that's laughable.
My brother is getting it so i'll play it through when hes done. I'm in no rush though. I'd rather play with keyboard and mouse. Maybe I can wait 4 years for it to come out for PC.
Edit: Just checked, it was gamespy that said 11-18 hours for SP.
http://xbox360.gamespy.com/xbox-360/.../821976p1.html