I don't think he is, nobody really stays dead on Supernatural. By seasons end, Bobby will be back along with Castiel. I just can't see the two characters missing the rest of the season.

I think in an interview the actor for Bobby said he'd return, but not the way he used to be... Sam is supposed to be dealing with his hallucinations of Lucifer at some point, I'm betting there'll be some Bobby manifestation there, and maybe Castiel as well.

An evil Bobby return plot twist would be awesome. Even better, if by the end they get him back normal.

Some of my dream figures would Neca Sam n Dean.

I might end up though doing these one of these days: