https://www.youtube.com/watch?v=7jjqUZN5IDQ

Star Wars Explained made a pretty neat little speculations video about the new BTS reel.
Some of the stuff he talks abut has laready been discussed here; like Bail Organa on Yavin, Jyn and Cassio going undercover as Imperials, etc.
But he also makes some interesting speculations as to Galen Erso’s role in the film and the relevance of the planet Jeddah (the sandy place where we see the tank) to the movie and the new canon.

EDIT:
Also from what I’ve read (it was also speculated in the video above) we will get too see a young Jyn Erso, implying that RO will either be the first SW movie to have a flash-back (which makes sense since it’s an anthology film) or the film will start several years prior to ANH and then cut to when Jyn is an adult.