He should follow Bob Kennedy's example and train with the Africans.
If he does not run at least a 3:52 mile within the next few years then he should be concerned.
Remember, Jim Ryun had already set two world records when he was twenty years old. Webb is obviously not developing at the same rate as Ryun was.
I still believe Webb may run a 3:49 mile someday. You cannot ignore that 3:53 he ran in High School. The talent will eventually have to blossom.
I don't think Steve Scott will be topped by another American miler for at least twenty more years. No American has really come close to the 3:47 mile Scott ran in 1982. The only way I see this record falling is if a talented African runner becomes an American citizen.
In conclusion claiming Webb finished at 20 years of age is a little extreme. He is just not going to be the next "great" US miler. However, I can foresee Webb becoming a powerful US miler in the vein of Jim Spivey. I do believe Webb has enough speed and strength to run a sub 3:50 mile someday. Believe me the US needs a miler with that speed desperately.