Since this is leading RIGHT up to the beginning of A New Hope, it'll probably end with the Rogue One crew successfully transmitting the plans to the Tantive IV with Leia on board and show her briefly acknowledging that she has them. Most of them will probably get killed, but they'll get those plans sent first. I think that trailer shot of Jyn limping when the Tie comes up is her transmitting those plans right before getting killed.

As for the Ghost crew, I really doubt we'll actually see any of them. Really cool that they put that ship in there though. At most maybe we'll hear Hera's voice over the comlink checking in during the battle. Since Rebels is currently around 2 years earlier in the timeline from Rogue One, they don't want to basically spoil Rebels by showing Ghost crew members alive at the time leading up to A New Hope. By that point in the Rebels timeline, I would expect some of that crew to have been killed, or no longer fighting with the Rebel Alliance (especially Ezra and Kanan, and probably Sabine and Zeb.)