Some predictions for the next arc and beyond:

The climax where Quirrell's identity and/or motives are revealed will be in the next two arcs (p ≈ 0.8), and possibly in the next arc (p ≈ 0.3).

This last arc ended ominously; I think we're perilously close to seeing some serious shit. I assigned low probability to this happening in the next arc because Eliezer said the next arc picks up immediately after this one. We're still in April, and I have this hunch that maybe Harry's "What do I get if I can make it happen on the last day of school?" line to McGonagall was foreshadowing. I also think we'll get to see Quirrell execute his Christmas Wish plot. And speaking of Quirrell plots,

Quirrell will execute his Final Solution to the Granger Problem in the next arc (p ≈ 0.75) and very possibly succeed (p ≈ 0.5)

The next arc is going to pick up immediately following the last one. I assume that "immediately following" means "the day after". Quirrell might have given her more than one night to consider if he weren't planning on getting rid of her immediately. If seers all over the world have nightmares one night, then presumably something bad is going to happen very soon thereafter. Hermione meeting (or maybe even almost meeting) a horrible demise would send Harry straight to his Dark Side, and who knows what he'd do then.

The worldwide seer activity is due to Harry being about to kill a lot of people. (p ≈ 0.35)

Harry Potter's Dark Side just figured out a reliable way to kill large numbers of people in a small amount of time. Maybe he's about to use it.

The Trigger Warnings are next going to be updated for a chapter called Gur Olfgnaqre Rssrpg. Vs n ohapu bs crbcyr jngpu Urezvbar trg uheg naq yrg vg unccra, Uneel zvtug qrpvqr gurl nyy arrq gb qvr.

Or, if you connect Harry's two unwittingly ominous resolutions that directly preceded the two Trelawney nightmares, he might decide that everyone in Britain who supports Azkaban's use of Dementors needs to die. All he needs is a broadcast medium to disable the country's Patronuses, and he can send a Dementor to create a wizarding holocaust.

I assign low probability to this not because I think the clues don't point reasonably strongly in this direction, but because I fail to see how Harry and the story could recover from it. Perhaps Dumbledore would subdue Harry and take him into hiding? But then we wouldn't see the end-of-year stuff at Hogwarts, unless it happens two or three arcs from now.

At some point, Harry will break his Time-Turner to get out of a sticky situation. (p ≈ 0.85)

Twice in early chapters we were told that strange things happen when Time-Turners are broken. Once would be an offhand reference, but twice indicates to me that Eliezer has something in mind. If Harry successfully rescues Hermione from whatever Quirrell tries to do to her next, I think this might be how.

Those probabilities are mostly pulled out of thin air, but I've seen other people use them, so apparently it's expected. Is there some systematic method people use to arrive at them, or do you just sort of look out a window and see what number feels right?