And they brought Sara back from the dead somehow.
So this means that both the Flash and the Arrow are going to be in two different series going on simultaneously? Or are they just sorta backups that introduce the other characters and then just pop in on occasion like they've been crossing over on occasion this past season?
The latter. They're there to set it up.
They show her coming out of the Lazarus pit in the trailer.
While Robbie Raymond isn't involved, I hope he's a regular guest start.