They used to have this info on the member web site, but since it's been "upgraded", they're not there any longer. I have, in the past, used Travelocity or Expedia to get the rack room rates for the dates I've been interested in. The member discount rates are usually only available (if at all) a couple of months before the reservation date. Disney Visa rates are only available for very limited amounts of time, during the slowest seasons. They're usually not announced too far ahead of time.
It's frustrating sometimes. I usually just look up the rack rates, and figure it as a "worst case scenario" and hope that something better opens up later on!