Whew, it's a bit early for this question, but I'll take a stab at it.
Sebastian Aho has to be considered a front-runner (especially if he can figure out how to find the back of the net in October - watch out); in fact, he was probably a part of the conversation last season, as well. I'd also give an outside shot to one of Andrei Svechnikov or Martin Necas if one of them blows the doors off in the first few months of the season.
But, as you mentioned, the Metropolitan Division happens to be stacked with talented forwards, and the Canes happen to be stacked with talented defensemen. Barring injuries, Sidney Crosby and Alexander Ovechkin are locks to occupy a third of the Division's forward roster spots. Though, with John Tavares now in the Atlantic Division, perhaps there is more wiggle room at forward.
If the Canes' All-Star representative is again a defenseman, Dougie Hamilton would be a good bet. After all, NHL Network pegged him as one of the Top 20 Defensemen in the NHL. Depending on the start of his season, Justin Faulk could also be in the discussion, given that he's made four previous All-Star appearances.
After having only defensemen represented in the 3-on-3 tournament, it'd be nice to see what a Canes forward could do in that format. We'll see! Ask me this question again in December when my prediction can be more informed.