In the video, Gad lures Ridley into his trailer under the pretense of preparing for the days filming.
Its about todays scene: Who are the last Jedi?
Ridley shuts him down immediately, replying, Were not doing this, Josh.

Credit: David James/2015 Lucasfilm LTD.
Is it one [Jedi], or is it more than one?
I need it to to get to figure out what were doing on the train today.
So is it plural?
… Is it ominous?
Does something happen to you and Mark [Hamill], or just Mark?
Are you a Jedi?
Answer my damn question, Daisy!
Alas, it seems Gad will have to wait till Dec. 15 to get the answers he seeks.
Watch his video below.