Younger versions of these characters have been shown in other instalments of the franchise. Jean was seen as a young girl being visited by Charles & Erik in Xmen: Last Stand; Storm seen when Charles & Erik were searching for mutants in Xmen: First Class & Scott is seen in Xmen Origins: Wolverine when Sabretooth captures him from the high school, here is what those versions looked like.
& Here are the versions we are used to seeing
& The new cast who will be seen in Xmen: Apocalypse which is set in the 1980s.
Now I don’t think I have seen any of these actors in anything, but I find at least the actress chosen for Jean has the look, the other two do somewhat as well. I will definitely write a review next year when the film comes out as well as keep everyone updated with any xmen news.