According to sources around the Internet, Disney will begin implementing a new booking system that combines dining, recreation and tour bookings into one system (finally)
The implementation will start on July 21, 2008->October 24.
Perhaps most important to note is that while this is taking place, the latest dining date which can be booked in advance will be January 25, 2009. Once the new system is operating, it will revert to the 180 day Advance Dining Reservation window.
The exceptions to the shortened ADR booking window are Cinderella's Royal Table, Chef Mickey's and Victoria & Albert's.
*UPDATED* - Dawn found this, which seems to fit. Could this be the reason for the new system?
Disney have sent out an email to Travel Agents informing them that Travel Agents and guests will soon be able to book dining reservations online. Here is the quote from the email.
"In the future, Travel Agents and Guests will be able to make dining reservations online at disneyworld.com with this new reservation booking system. The launch date for this enhancement will be announced at a later date."