I think the idea of overlap with Star Wars is a distinct possibility.
I frankly don’t see “how”. No life form escapes the Tantive IV. Leia’s got the plans and clearly puts them into R2. Everyone on board of the Tantive is either killed or made prisoner. It’s supposed to be a diplomatic ship, so no obvious members of the Rebellion (i.e. the death star suicide squad) would have boarded it. There is already no need to tell this story, so I don’t think at all they are going to step on ANH.
On a screenplay point of view I don’t have any hopes about this reboot/prequel; but the director knows how to shoot action scenes and how to create suspense. He’s also got a very good visual style (Godzilla 2014 is not a great movie at all, the script is lazy, the main protagonist isn’t interesting, but there are a few dazzling ideas). So at least Rogue One could be visually interesting and, why not, surprising. If I get a mediocre/average movie, it will be more than I expect.