In terms of converting potential, they've not exactly been helped by a succession of managers who were either reluctant to give young players a chance or were so crap that they mis-used them and the side was poor. Provided that Lambert can stick around for a good number of years and the philosophies and infrastructure that are put in place during his stay remain, we should see promising young players adapt to the first team.
I know what you mean but there was massive interest in Luke and we had to ensure he stayed. Hence his first pro contract being larger than typical. Maybe the size of the contract contributed to his attitude problems which is the only thing stopping him from being a top player. It still annoys me greatly how spectacularly he has bombed when players with a fraction of his natural talent are thriving.