Maybe. Pitino and Smith both took already-premier programs and kept them at that level (and Pitino, at least, cheated). Knight was a product of his time, and only had about 10-12 really good years before a steep decline. I put Izzo's accomplishments over the past 20 years up with Knight's and am willing to lose the argument, but I really do think it's an argument.
I mean, 7 final fours in 18 years, including 3 in a row, is pretty amazing. And he's never really had a GREAT recruiting class until the one coming in next year. I wouldn't be shocked if he put something remarkable together over the next two seasons, even without Valentine.