I've read a lot of codas to this episode (I haven't seen an ep produce so many codas since "Mystery Spot"!) and wow, the consensus seems to be that FutureDean is way beyond damaged. Which is not exactly how I read him. Yes, he was broken and kind of a jerk, but really in ways that just exaggerated flaws Dean has in the present. (This is not really in response to what you said, I know--your comment just gave me a convenient opportunity to rant about people making futureDean into a dograping babykiller. Or more accurately, a Castiel and/or pastDean-raping minion of hell.) But futureDean also had presentDean's leadership ability and drive exaggerated as well, and those are generally good qualities.

Anyway, I totally believe Sam and Dean can save the world if they work together.