Having gathered all the internet evidence I shall place my no-money bet!
Official debut Tuesday, July 8
Soft open Sunday, July 6
Why? Disney has a history of debuting things on Tuesdays and Fridays (idk why those days but they do). Two days of soft openings accessible to the general public happened with Harmonius and one day of a soft opening with 50th Fireworks so not unprecedented. CMs continuing blackout practically confirms it will be running over the 2nd week of July. Moving 7/2 EEH to AK indicates something happening at MK, no reason to move it otherwise, however the fireworks not moving until Sun leads me to speculate parade testing after park close.