I wouldn’t be surprised if Palpy shows up for more senate scenes to be honest. But the plot will probably revolve around them trying to find out what the super weapon is, to follow up the post credits tease. Plus they will have to find a way to lose characters who aren’t in Rogue One and deliver others. So bigger fractures between Saw and the Alliance, a reason to get K2 on board, the likely death of Bix and Vel. Maybe the defection of Galen Erso and the training of Jyn could be involved. What is the time frame?