I tend to agree, even if an oversimplification. Not too long ago you have Arizona, Oregon State and UCLA regularly showing up in CWS and winning them, mainly with California players. I guess the exodus out of there really took a toll on the 'sports-playing' class of the state.
Even with that, I don't think it's ALL about the exodus of people. I think those California and West Coast players are just wanting to head to the South, because people care more. Just like football.
And THAT is what's puzzling to me. Football and baseball has (or had) declining youth participation numbers, and you also are seeing the consolidation of power in the South. But at the same time football is gaining popularity (both college and pro), while baseball is declining. It's hard to figure out what is really going on here.