That's changing in a major way with the third installment, however, given that the upcoming and untitled Jurassic World 3 is reuniting Sam Neill, Laura Dern, and Jeff Goldblum to work alongside the more recent franchise stars. And the reason why that's only happening now, according to director Colin Trevorrow, is because this is the story that has discovered the way to organically bring everyone back together.
Jurassic World 3 hasn't actually started production yet, but the filmmaker recently spoke about the production with Empire, and in that conversation touched on why now is the time to bring back the original Jurassic Park stars. Seemingly recognizing how Jurassic World very much echoes Steven Spielberg's original 1993 movie, Trevorrow explained,
J.A. Bayona's Jurassic Park: Fallen Kingdom, the last chapter in this franchise, notably tied the newest era back to the original with the inclusion of Jeff Goldblum as fan favorite character Ian Malcolm – but he was entirely separated from the action in the movie. The part involved him testifying in favor of letting the surviving dinosaurs of the world go extinct, and that sequence was split up and featured at both the beginning and end of the film. He was a notable presence, but hardly a key part of the plot.
With Colin Trevorrow saying that Jurassic World 3 is basically Jurassic Park IV, we can assume that not only will Ian Malcolm have a much more significant part to play (which would be the the first time since Steven Spielberg's The Lost World: Jurassic Park), but obviously also Alan Grant and Ellie Degler nee Satler.
Colin Trevorrow has co-written the script for Jurassic World 3 with Pacific Rim: Uprising writer Emily Carmichael. Universal Pictures has already announced that the movie will be hitting theaters on June 11, 2021, so expect production to start up in the first half of next year.