Information
For most purposes this Dean will be portrayed at the end of S5, a few months after moving in with Lisa and Ben and before Sammy comes back. It might make him a little more of a jerk at times, but for the most part he'll still be the sarcastic, slightly quick tempered Dean he always is.
Another note to make is that under no circumstances will there be any shipping, sexual or romantic interactions for Dean. While he will make his flirtatious comments there is no intention or desire on the player's part to interact this way with other people and thus there will be no actual interaction or relationship that grows from those comments.
I will keep him ic, I know his ways just he will be single and ic. If this bothers you or is not what you are looking for then it is best to find some one else to play him for you.
This applies to handwaving situations as well, there will be nothing, not even the illusion of a relationship between Dean and any character.