I think I prefer "original thinkers" to "polymaths," and I don't think that educational systems have much to do with it. I think it's more genetics, inspiration, and opportunity, in that order, that make the most difference. I don't think that we all have polymath tendencies, and I'm doubtful that educational systems make that much difference.
I think that the most important facilitator to growth is through networking--and networking opportunities are probably the greatest they have ever been.
Best evidence for such facilitation comes from the "hole in the wall" experiments: