Following up on myself WRT Sam still dealing with the Jessica thing even into season five, and not just the beginning, but again at the end after the Brady reveal. Anyway, remember how much of the first season we saw Dean trying to comfort Sam about Jess, John being all understanding about Jessica's death, and how many times the Jess thing was brought up by Sam in that first season. Yet they managed to do that and still have the brothers have a relationship and get closer.

So if the writers want to be fair and care about how it's going to look when Dean leaves, they can still have the brothers being happy to be together with Sam being the one to offer the shoulder this time whenever Dean misses Lisa and Ben.

I'm assuming - probably shouldn't do that - that one reason Dean leaves to go back to the hunt is that it may be dangerous for him to stay with Lisa and Ben given whatever the heck is going on that requires the boys to hit the road again.