I believe they will retain their SB memories, but things will obviously change, since they will get their memories back. What will all the former kings do, once they realize they are no longer kings?
Although I believe alot of the townsfolk will want to string up Regina, and we may see them come very close to killing her, I believe she will find a way to keep herself alive and well as long as she has something the people of SB need. She may convince them that if she dies, they all die, and that no one goes back to FTL. My thought is, the people of SB will divide into two factions, those that want to go back to FTL and the magic,and those that perfer their new lives in SB without magic. The people that were afflicted with issues in FTL (stuck in a mirror, turning into a wolf, being a dwarf committed to mining) may want to remain in SB.