Not that high. Prospects in general that arent superstars have a very low chance at making the nhl. All the guys that you mentioned who are in that lindgren tier like Duszak, kokkonen (who is probably better), Hollowell and Kivihalme all have a very low success rate. It's far better from an organization's standpoint to go for a machine gun strategy and turn them into the best possible player they are capable of becoming. At the very least they all become good AHL defenseman that help the marlies compete for a title but they also could have some good seasons and become trade pieces with decent value. No matter what happens to him, guys like him can always be traded for future considerations but theres absolutely no risk in developing him