They are adding more tiers, moving to a day-based system rather than a credit based system. No one is losing a level (so, if you are Diamond now, but would not qualify as Diamond under the new system you keep Diamond status but cannot move up to D+ until you qualify under the new system). They are adding amenities, added new rewards for referring a friend.
There is no buy-up option. No one is losing a level although for many it may be more difficult to advance to the next level.
Look for changes January 12, 2011! Look for the press release sooner. I love knowing folks in Loyalty. The new colors are pretty