I was there last night and you can't get from Autopia to Small World without going to the castle. I'm not sure if that wall is coming down before Thanksgiving (ETA for return of Matterhorn), but unless it's to block the view of an empty lagoon, they should be down by Christmas. As for the walls in Adventureland at least by the Tiki Room, they'll be around until early next year. MousePlanet seems to be doing a very good job tracking the downtime schedules.
BTW: Be sure to see Small World Christmas, Haunted Mansion Christmas and the Fireworks Show, they are all quite magical.