The newest entries in the Jurassic World franchise have the potential to bring back even more characters from the original Jurassic Park trilogy. Both the animated spin-off series Jurassic World: Camp Cretaceous and the upcoming third film Jurassic World: Dominion feature characters from the original trilogy, but there are individuals that haven't been announced yet that could still make an appearance.
The original Jurassic Park was a landmark moment in blockbuster history, both in terms of how popular the movie was and how much it pioneered CGI special effects. Steven Spielberg's 1993 film spawned two sequels, each with decreasing popularity and quality. A fourth film was in development for over a decade, until a soft reboot came in the form of 2015's Jurassic World. While the movie had mostly a brand new cast, it was still filled with references and callbacks to the original movie. It even brought back BD Wong's Dr. Henry Wu, who had a minor role in the first film but a larger one in the World trilogy and the cartoon. The sequel then had a very brief cameo from Jeff Goldblum as his character Dr. Ian Malcolm, and Dominion is selling itself on bringing back Malcolm along with Dr. Alan Grant and Dr. Ellie Sattler, again being played by Sam Neil and Laura Dern respectively.
This begs the question that if the new movie is selling itself on bringing back legacy characters, then what other characters from the original trilogy could make an appearance? There are a number of characters who survived the first three films who could do anything from having major roles in the new movie to simply making cameo appearances in it, or in Camp Cretaceous. There are ones that seem like obvious picks, but others are less obvious yet can bridge the gap between all the entries in the Jurassic Park franchise.
Tim and Lex Murphy
The kids from the original movie seem like a clear choice for legacy characters to bring back, especially since they'd both be adults by now and would have the familial connection to John Hammond and the Park's legacy. Tim even had an active interest and knowledge of dinosaurs, so even if his sister would never want to return to Isla Nublar he could still be tempted by all kinds of new dinosaurs.
Dr. Sarah Harding
Ian Malcolm's former love interest at the time of The Lost World: Jurassic Park, she's still an accomplished scientist in her own right. She specialized in animal behaviors, including that of dinosaurs, and could possibly take an interest in the genetically engineered creatures that have escaped from Jurassic World. The only issue would be that she's played by Julianne Moore, who may not have much interest in reprising her role for a small/cameo appearance. It's why it's unlikely for someone like Vince Vaughn to reprise his The Lost World character either. She could potentially be recast and appear in Camp Cretaceous.
Kelly Malcolm
Ian Malcolm's daughter seems like another obvious pick. She probably wouldn't have a major role of any kind, but her and her unseen siblings could make a cameo in the film as they would still be a part of Ian's life at the time of Dominion's story.
Billy Brennan
Billy was Alan Grant's assistant in Jurassic Park III and was believed to have died from a pteranodon attack, but he actually survived. He could be a character who can appear in the cartoon show, possibly as an experienced guide or mentor to the younger heroes.
Eric Kirby
Eric was the boy who Alan Grant saved from Isla Sorna and who he formed an emotional connection to. It's unlikely he would play any kind of major part in new stories, but he could be seen keeping in contact with Alan Grant at the time of Dominion, just as a nod to the series's history.
These are just some of the characters from the original Jurassic Park trilogy who could make appearances in new Jurassic World installments, each of them being an opportunity to honor and acknowledge the history of the franchise.