On the positive Side, there is no new Project listed for Robert Carlyle on IMDB, that would take him away from the Show. If he had a big project that was known, that could really lower the chances they'll bring him back next half-season.
Of course absence of proof, is not proof of absence, but, at least it is a lack of proof that he has something big coming up, so there's hope.
I think they have their memories, only Emma and Henry lost theirs, and Emma was given a memory of keeping Henry and living through his infancy to childhood, which would allow them to live happily ever after and give her a reason to have this child with her now. As mentioned upthread, it wouldn't be as much punishment for Regina if she was able to forget her pain in losing Henry forever. The curse was destroyed, so it didn't take the memories of the Fairy Tale Characters.
Hook, is not from the Enchanted Forest, so, he went to his place of Origin, which I believe, allowed him to work his way back to our world and find Emma in the year that has passed in the time jump.