What's making me think that they might have at least had a notion is that there are only three eps between this one and "Sympathy for the Devil" (S5 opener) wherein Dean is revealed to be the Michael Sword. Yes, there was the summer hiatus in between, but I wonder if they were starting to hash it out at this point. They would have had to have had some sort of notion where they were going because their storytelling time would have been limited.

It'd be an interesting question to ask, though I'm not sure we'd ge a straight answer from them at this stage in the game.