The thing about the Andrew Scott returning for S3- It can’t just be Moran finding the body.
Because they had the foresight to film Benedict and Louise’s scenes with Molly and Sherlock coming up with the whole deception/fall scenario back when they did S2, so that they would look exactly the same and the continuity would stay intact.
I don’t think it’s unreasonable to say that if there’s been any shot of Moran finding the body on the rooftop, or any shots of dead Moriarty, they also would have filmed those scenes on the day they did the rooftop scene, because the body couldn’t have moved at all.
Whatever they’re filming has to be a flashback or some sort of psychosis on Sherlock or John’s part (or Moran?).
Unless… Jim isn’t really dead?
Either way, it’s nice to get some new news, FINALLY.
I’d say the first two options are most plausible, though. He looked pretty dead.
But then again, so did Sherlock.