I've given it some thought, and here are my predictions/hopes for 2020.
- both Mitama and Yozakura survive, hanging around the lower middle range like early Jujutsu Kaisen
- Chainsaw Man has an anime announced.
- Jujutsu Kaisen's sales jump due to the anime announcement/potentially anime airing, and Western reception improves due to that and the official release of earlier chapters of the series, previously unavailable legally.
- Act-Age has something live action announced first, with an anime potentially being announced at Jump Festa.
- Samurai 8 climbs high enough in sales that we stop hearing (or at least they stop being posted as often) the wailings of "Samurai 8 is getting axed next week, my uncle's cousin who works at Shueisha said so".
- Yuuna ends around the middle of the year, but thankfully pulls a To Love Ru and starts the Yuuna Darkness arc in Jump SQ within the next two years, receiving a considerable sales boost, back up above its prime in WSJ, when it does.
- The Black Clover anime will end once the current saga they're on is fully animated. The manga, however, will sadly not receive any sort of boost in sales or recognition despite only getting consistently better as it goes along.
- Agravity Boys will be axed after 3 volumes, but in an ironic twist, Zipman will receive a recommendation by Horikoshi and survive the year.
- Dr. Stone finishes the current arc, and its final arc is announced, which will run for another 1-2 years.
- My Hero Academia gets a small boost once season 4 really gets to the good parts, as well as the movie coming out.
- We Never Learn ends between February and March, with none of the girls winning the Yuigabowl.
- The current arc of The Promised Neverland is dragged out longer than we actually thought it would be, but still ends by April at the latest.
- One Piece's Wano arc enters it final act, but it still does not end this year.
- Haikyuu!'s sales will pick back up a bit with season 4 airing and hype around the "final" arc.
- Kimetsu no Yaiba doesn't drag its feet in ending, and takes the AssClass/Kuroko route, ending at the height of its popularity.
- One prolific veteran will return, and another "veteran" who has only had flops will return and make a hit for themselves.