Byron will likely be traded before his deal is up, considering the young players coming into the lineup. I don't see him being moved this year unless we're either completely out of it, or a young player like Suzuki or Poeling firmly establishing themselves as a top 9 force. Not that either player will directly take his spot but their emergence would create a domino effect that would make him expendable. I don't see either of those things happening this year before the deadline.
To me, he likely stays and is moved for picks in the offseason, just like Shaw. But for this year, he's a valuable guy that can play and produce at a decent clip anywhere in the lineup. He's been averaging 20+ goals for 3 straight seasons and is an excellent PKer and OT guy due to his speed.
If the Habs go for Puljujarvi I see it being more likely for another young player/prospect. ie Juulsen, Brook, etc. I could see them taking a shot at him just because we do have Finns here and at least part of his issue has been language and feeling comfortable in the room. I think he could do well on KK's wing. However, I can also see the management being concerned that he could be a poor influence and not loving his attitude.
I hear the Gallagher/Caufield/Suzuki depth argument but I'd say when you have a player that has this kind of potential, you go for it. Caufield I can see being a good LW. Suzuki I think might be a better C than RW, and if Pulji works out, he gives you a dimension that doesn't exist elsewhere in the lineup - a big, RH, winger who can score from in tight and play with elite players.