When speaking with The Daily Beast, Ryder did drop some hints that she will be part of the sequel. That is if both Tim Burton and Michael Keaton are on board as well.
"I’m kind of sworn to secrecy, but it sounds like it might be happening. It’s not a remake, it’s 27 years later. And I have to say, I love Lydia so much. She was such a huge part of me. I would be really interested in what she is doing 27 years later. I would never go near a sequel if it was not Tim and Michael because those guys, I love.”
This is plausible because it apparently takes place 27-years after the events of the first film. Ryder was 17 when the first movie was made so this would put Lydia pretty close to her real age. Plus, if she has this information and it's actually true this proves that she has at least read a draft of the script. If she does officially join this project and Burton is directing it will mark the fourth collaboration between them. Ryder previously appeared in Beetlejuice, Edward Scissorhands, and Frankenweenie.
Aside from Keaton and Ryder, other cast members that could realistically return are Catherine O'Hara and Jeffrey Jones. Personally, I would love to see O'Hara as Delia once again. I don't see it as feasible to expect Geena Davis and Alec Baldwin to return as the Maitland's, though. This is due to the sheer fact that their age would make their characters ridiculously unrealistic. Ghosts don't age. Period.