They kind of hit rock bottom in 'Croatoan' in S2 as well and Sam was giving into despair pretty heavily back then too! We all know, that they like to make things worse before it goes up again! *g*

Well, they killed Sam, see how that turned out! *lol* Honestly, no matter how they go about it, this show only has 2 leads and they won't have a show with one of them dead. There is no way in the world they kill Dean off for good. ;)