To follow up on an earlier post:
The FAA’s doctrine on airspace is on the web at http://www.faa.gov/ATpubs/AIR. Regarding Class B, see chapter 15, section 15-2-3. The standard profile for new or expanded Class B airspace includes an upper ring of 30NM radius with a floor 5000-6000 feet above the airport surface and a ceiling of 10,000 feet.
In the future, expect to see more Class B with 30NM maximum radius. 20NM isn’t the standard any more. Will they use the current situation to advance their agenda for airspace redesign? Anybody’s guess. See also the NAS Evolution plan at http://www.caasd.org/nas-evol/.