Well... I'm not sure what time frame it would create more GC contenders in.
I know for many sports in the US, you get slotted at a very young age. I started swimming competitively at 6, and by the age of 13 I had missed enough of the "prep" stages for other sports (little league baseball, AYSO soccer, pee-wee football) that I was almost locked out of really getting into those sports.
I can't complain... I was very successful in swimming. But I don't know that at 21 (my age when Lance won his first TDF) I COULD have switched to cycling even if I had a natural talent. My training had been so developed toward swimming that it would have been very difficult to switch successfully. I'm not sure I could have made that jump at 15... I already had almost 10 years of physical development geared toward strong lats and triceps, along with the wrong sort of strength in the legs.
I would think any effect on creating true top-level talents for cycling that wouldn't have gone into cycling otherwise would be amongst people who were fairly young around Lance's first tour... maybe aged 10 or less. By the time Lance had a few TDF wins under his belt, those kids would be 12-13... still young enough to perhaps not have been drawn completely in to another sport.
So really you're looking at guys who'd be 20 or younger right now. I think it's too early to see if they are really going to be good, but names to look at would be Stetina, Phinney, Van Garderen, East, King, Kuphaldt, Campbell, Selander, Busche, Talansky and Bradshaw.
How many of them will be successful on the higher levels? How many were inspired by Lance in some way? I have no idea.