Theory: there is no HIStory 25 because there isn't enough material to warrant one.
Several informants have suggested that the HIStory section of the vault is essentially barren. Neither Joseph Vogel, Damien Shields, nor Mike Smallcombe—three of the most credible sources available—have been able to identify a single usable outtake from the 1994-95 sessions; several of the long-circulating titles (e.g., "Bassouille," "Fear") have been debunked; and the handful of known titles are either released ("Morphine," "Is It Scary," "On the Line," "In the Back," "Much Too Soon"), spoken word pieces over instrumental grooves ("Faces"), or lacking vocals beyond a chorus ("Willing & Waiting," "Innocent Man").
Assistant engineer Rob Hoffman did say there were a few nearly-finished pieces in 2009, but since he refused to identify any titles beyond "Much Too Soon," it's within the realm of possibility that these were holdovers from previous albums that we've since heard (e.g., "Do You Know Where Your Children Are").
Furthermore, are the demos of HIStory tracks even worth inclusion? Early cuts of songs like "Jam," "Billie Jean," and "Gone Too Soon" are completely extraneous, and that very well could be the case here. "What About Us" is nearly indistinguishable from "Earth Song," and for all we know, the 1989-90 sketch of "They Don't Care About Us" has no vocals.
When the Estate was gearing up for Off the Wall in 2016, they issued a statement claiming that there was insufficient unreleased material to justify any sort of elaborate music drop (which is entirely plausible seeing that the Off the Wall sessions are just as desolate as HIStory in terms of publicly available information). That very well could be the case here.
Plenty of fans were displeased with Bad 25 because it housed the two foreign language cuts of "I Just Can't Stop Loving You" and three irrelevant remixes. If all the Estate has to offer are similar recordings, maybe it's best that we don't get anything. I'm sure plenty will say, "the Estate is just greedy," but sometimes that's not the case.