And HMH has been running since September, so that will be up too. But as far as a soft opening for IASW, it's highly unlikely. Disney has been doing this overlay for years and they know how long it will take.
Last year the Jingle Cruise overlay consisted of the skippers wearing jungle santa hats, a wreath at the entrance and holiday music in the queue. We were told there would be holiday jokes, but I rode it twice and didn't hear any. There were no decorations on the ride itself, but since it was the first year, they may do more this year.