I agree that Coyle likely would have still had a good NHL career if he had stayed at BU. He had a very solid freshman season, he was just in a rut the first half of his sophomore season. I'm not so sure about Bellows. He did NOT have a good freshman season, at least good enough to show he is a future NHLer. His biggest strength was supposed to be his shot, but he wasn't able to create enough space for himself to really leverage it.
I really hope he finds success and makes it, but I have my doubts. I think he would have developed into a good college player had he stayed. Beyond that, who knows.