Grand openings of both Pandora and Toy Story Land have been/will be on Saturdays (too lazy to look back to see if that has been common in the past, but I'm guessing it will be that way for Galaxy's Edge). Since Nov 9th, 16th, 23rd, and 30th are all taken, I'll predict:
December 7th, 2019 (just a hair under two weeks before Episode IX comes out)