I'd also think the end of the campaign won't cause any harm between the players. Except maybe between the GM and the players but that's only natural
For the future, just as Icedaemon (if I understood correctly) I suspected Annie to become the GM for a while since it would easily let her play Vader in the next campaign. There's not much to argue against people staying with their current characters, Pete as R2D2, Sally as C3PO/Yoda, Ben as Obi-Wan. Though We probably need new players for Jim and Han, probably Leia, too. The old GM make pick up one of those, but unless some is going to dual play two characters, there's no way around at least one further member. They can't all be NPCs.