No way, no how, is Bobby Singer gone. Even though strangling the writers (or remedial English class) is often considered for some shows,including this one, I do not want to believe that Ben Englund would heave so many "Bobby's gonna die" anvils in the very episode were Bobby dies. He's better than that. And while yes, Bobby dying would light the fire under Dean's ass to get him back in the game - couldn't we just have Faith for that, anyway? - that would leave them with only each other. They need a third. They don't know how to function with a third, even if it is at a distance.
Besides, would Crowley really want his boyfriend dead?