Poehling might grow into a top-6 C. It's possible given the lift-off that his offensive game displayed in the minors, after he was drafted as more of a two-way guy. What I'm skeptical about is that he will step in and be a #2C next season, his rookie year. And even in the highly unlikely event that he plays like a top-6 FW consistently, it is probably more realistic that *he* would be the guy placed on the wing next to Domi, rather than the other way around.
Here's another way to put it: Poehling is 99% guaranteed NOT to be a better player, or better C, than Max Domi next season.
My general attitude can be summed up as follows. Rookies rarely step in and make a consistent impact. That's just reality. And that's why I generally don't get too excited about what they will add to the roster, in that first season. Call me a pessimist all you want, but the list of Habs rookies/prospects that people got all excited about is practically endless - and of all of them, only a small handful actually bucked the odds and had an immediate impact. (Indeed, most of them amounted to nothing or relatively little as NHL players in general, never mind as rookies).