It was Epcot on the well used 5K route running through the parking lot, backstage around the WorldShowcase, under SpaceShip Earth and finishing at the half and full marathon finish line. The last year for this course was 2006 when Disney split the half and full marathons over two days. Logistically it just didn't work well to hold the 5K after the half on Saturday any longer. In 2007 it was moved to Disney Studios and will be in AK this year.
I do not believe the 5k will keep a rotating schedule of venues but that it is looking for a home that serves the fast runners well. i.e. fewer sharp corners, flat and straight. The AK course seems a little better than the Studio course in that regard but I would look for the 5K to have a different home at some time. Where it will be in the future is anybody's guess. Maybe it will move back to Epcot again if Epcot management can be persuaded to deal with the aggravation of three races in three days. If you want to see a map of the course look at the Kidney Transplant Page on the WWoS page. That is the old Family Fun 5k course.