I like Bobby, but it just doesn't make sense to keep him around anymore, at least from a plot POV.

I want to see Sam and Dean attempt to kick each other's ass, have Sam win the fight but choosing Dean above everybody at the end because if nothing else the Winchesters knows the bonds of blood.

Ohhh, I like your theory! See, my take on the whole thing is that they resolve their issues, and then the fianl seal breaks, which lead to Sam becoming Lucifer, and then we shall see the fall out in s5.

End of s4 is going to be Epic!