Re: bernard and rose
I want to see them too. I had come hopes for them when they were given a flashback epi. There are a few threads that the Desmond time-loop changed the course of events and that Rose and Bernard died in the crash. When Desmond time-traveled, he altered events so that Pikki survived (when they initially didn't) and R&B died.
I think that a more likely explanation is that it takes a lot of time and money to bring back bit players to Hawaii for only a few lines of dialogue. Probably didn't make sense for TPTB to bring em back until they have something substantial to say or do.