He's a really good player. Watched him quite a bit this year, I see him easily going top 10, maybe even top 5, but it will be interesting to see how he does next year, as Brock mentioned above, the Generals are losing most of their top talent, so Dal Colle is going to be relied heavily on for generating a good deal of Oshawa's offense.
In the NHL, he's got all the tools to be a first line player. Whoever drafts him next year will be getting one hell of a player who can be a leader on the team and play in all situations. It's gonna be a great draft for the OHL next year (Ekblad, Dal Colle, Ritchie, Clarke, Goldoin, McKeown, McCann, Ho-Sang, Mistele, Middleton, DeAngelo, etc...)