Below is the full pre-opening Pandora schedule. Add 33 days and it may, or may not, give some insight into the TSL pre-opening.
Animal Kingdom CMs had the first previews followed by:
WDW CM preview, 5/5 through 5/12.
AP/DVC members, 5/13 through 5/22.
Press, 5/23 & 5/25
Dedication, 24th.
Random and limited soft openings, 24th and 26th.
Opened on the 27th