When I was at WDW 2 years ago the weekend before Thanksgiving, all the decorations were up. However, unfortunately none of the Christmas-type shows had begun yet-Candlelight Processional, Epcot Holiday Storytellers, Christmas tree Lighting Ceremony, etc. But I know people around me, who'd been there all the week before Thanksgiving were commenting on how crowded it was getting. I plan to be there the same time as you and I think it's going to be pretty crowded, especially the closer you get to the actual day of Thanksgiving.