I remember hearing talk about a Beetlejuice sequel years ago, and apparently Michael Keaton was more than willing to reprise the title role. At that time (and still now) I think it could work. I just hope it would be a true sequel, and not a remake/reboot.
Sequels to older movies can be tough to pull off (since the cast has aged) but with Beetlejuice it wouldn't matter so much. Under the makeup, Michael Keaton shouldn't look that different. Even if he did, you could explain that away with the fact that he's a magical ghost, and could appear any way he pleases.
I think it would be tougher to explain how Adam and Barbara Maitland (Alec Baldwin and Geena Davis) have aged, since they are normal, human-looking ghosts. Their story was told, I don't think a sequel would need them.
An appearance by Winona Ryder as Lydia might be fun, but overall I don't think we need to see the Deetz family back either. Sequels often trip up by trying to shoehorn every familiar character into a new plot where they're not really needed.
Beetlejuice is a mischievous ghost, selling his services as a bio-exorcist. The options for storylines are limitless. So I think a sequel would be best with BJ getting involved in an all new adventure with new supporting characters.
I'd love to see Tim Burton directing and Danny Elfman doing the score would be ideal, to give it the same vibe. And practical effects, not too much CGI. That would be my wishlist for a sequel.