I think Pettersson should stay in the AHL for the full season-- and I feel quite strongly about that. Puck skills and some of the quick defensive reactions/decisions necessary for NHL duty would be real problems for him right now. He's an okay second-pair AHL defenceman at this early stage, not a first-pair guy. A realistic progression would be to deserve call-ups next season and then hopefully stick in the NHL in the following season.
To be clear (I've said in another thread that I'd rather Pettersson than Juulsen), I'd prefer Pettersson stay in the AHL instead of pressed into NHL action or sitting in a press-box. I'm not opposed to him getting a game or two as the team has said they want to do with young players.