Yes, they should. I'm very excited about this movie, and bringing back Ripley and Hicks and potentially side-stepping the last two films is a dream come true. However, I've also long been an advocate of letting them go. One of the granchise's greatest weaknesses was it's inability to let Ripley go. I liked a lot of the old comics because they involved new stories, new people without connection to Ripley. I disagree heavily with those who say "the franchise can't survive without Ripley', because that mindset is what gave us Resurrection and weakened the franchise.
I believe Ripley, Hicks and Newt deserve closure, but after that, they need to retire and let new stories emerge within this vast universe. The franchise can survive and thrive without them.