I think JR wanted him build more of a foundation in the minors for half a season, especially because A. He had such a bad preseason and B. The drinking incident probably caused them to question his maturity, so keeping him down half a season let's him know they won't tolerate crap for the sake of talent.
So between those two things, hopefully Pouliot has realized what this opportunity means and takes it completely seriously. If he can be ok defensively and excel offensively, he'll be a very strong asset going forward. In my opinion, he's still the most likely prospect to be traded at this point. Obviously Letang is probably out tonight and Warsofsky definitely, but even still I wouldn't be surprised to hear that half the reason that tonight specifically they wanted to showcase him to St. Louis for a possible Shattenkirk trade.
Although to make a Shattenkirk trade work cap wise, we would have to part with Kunitz or Bonino in addition to Pouliot. I would suspect STL would want Kunitz more due to their desire to specifically target physical players, but Pit would be more willing to part with Bones. I think STL is so wrapped up in targeting players of their desired skill set, that they are more willing to forego a little trade value if it means more size/physicality.