I think television is prompting interest across the country at younger ages and softball is slowly becoming more a national sport than regional (California). Looking to the younger divisions there were many strong teams not resident on the west coast:
10U-A Nationals 2007
1st Indiana Thunder Goshen, IN 6-0
2nd 96 Diamonds Seagoville, TX 7-2
3rd Georgia Impact Red McDonough, GA 5-2
4th Florida Elite Haines City, FL 5-2
5th South Texas Riptide Lake Jackson, TX 3-2
5th Huntsville Comets 96 Huntsville, AL 5-2
7th Birmingham Thunderbolts Birmingham, AL 3-2
7th Victory USA 96 Laguna Niguel, CA 3-2
9th Birmingham Vipers Birmingham, AL 2-2
9th Downey Nemesis Downey, CA 3-2
9th Atlanta Vipers Douglasville, GA 3-2
9th Scottsdale Fever Scottsdale, AZ 2-2
Note that only 2 California teams placed in the top 10.
Going back two years, results from 10U in 2005 were decidely California-weighted:
1st Corona Angels Corona, CA 6-0
2nd USA Athletics Cypress, CA 5-2
3rd Lakewood Ladies Downey, CA 5-2
4th American Athletics Las Flores, CA 4-2
5th TNT Mustang, OK 4-2
5th Frost Falcons Chattanooga, TN 4-2
7th Missouri City Magic Select Missouri City, TX 3-2
7th Elite Panthers Orange Lilburn, GA 7-2
9th Atlanta Vipers McDonough, GA 2-2
9th San Jose Sting Campbell, CA 3-2
9th O.C. Wildcats Rancho Santa Margarita, CA 3-2
9th Salinas Storm Monterey, CA 3-2
There was more impact from non-California teams in 2006
1st 95 Texas Glory Mesquite, TX 8-1
2nd Downey Nemesis Downey, CA 5-2
3rd American Athletics Orange County, CA 4-2
4th Bomb Squad Anaheim, CA 4-2
5th The Groove 95 Austin, TX 6-2
5th All American Sports Academy Tracy, CA 5-2
7th Oklahoma Force 95 Mustang, OK 4-2
7th Deer Park TPS Deer Park, TX 3-2
9th Salinas Storm 10U Salinas, CA 3-2
9th Corona Angels Corona, CA 2-2
9th West Cobb Lightning Acworth, GA 3-2
9th Chi-Town Express Burr Ridge, IL 3-2
Looks like there is a trend. If it's valid to assume that players from these teams will continue their development (and remain in softball) it seems logical to expect higher levels of play from across the country in the next 5-10 years.