I only have a few things to add to your predictions:
1. Three “backbone” books will be published by Wizards this year, one in spring, one in autumn, and one in winter.
I think it's worth noting that the tendency for these books is that we always get one flagship adventure book made almost entirely in-house (Storm King's Thunder, Tomb of Annihilation, Waterdeep: Dragon Heist), a second adventure book, with a more contained storyline, that is either smaller or heavily involves outsourcing, and therefore requires less in-house resources (Curse of Strahd, Tales from the Yawning Portal, Waterdeep: Mountain of the Mad Mage), and one information book that compiles monsters from previous adventures and hints at stuff to come in the future (Volo's Guide to Monsters, Xanathar's Guide to Everything, Mordenkainen's Tome of Foes).
2. The autumn book may be a campaign-sized adventure, and it will be announced in early summer with a massive media kickoff event.
They could go one of two ways with this flagship adventure:
A) They go the safe route and release another Forgotten Realms adventure, either something based in another part of the Sword Coast or, hopefully, somewhere to the east. I'd love a more Thay centric storyline.
B) They could make the jump into a more risky venture and publish a Planescape or Spelljammer adventure, which would build a strong foundation for campaign setting hopping and enforce their effort of bringing their other campaign settings into the fold.
Either way, this adventure will most likely be in the 1 - 11 character level range.
3. The spring book may either be a new book of player options like Xanathar’s Guide to Everything or a book that combines interest for players and Dungeon Masters, like Volo’s Guide to Monsters.
I want to believe that we'd get a book that focuses more on player options, but we've been getting too few Unearthed Arcanas lately to believe that this is the case. I remember we were bombarded by Unearthed Arcana articles prior to Xanathar's Guide to Everything, and that doesn't seem to be the case this time around. Maybe we'll get a psionics heavy book if Mike Mearls' Happy Fun Hour streams are a hint to anything.
4. The winter book may be a companion to the autumn adventure.
Maybe. I do believe the "second adventure" book will definitely bring something that their flagship book won't in order to appeal to everyone in their yearly lineup. I do know that this secondary book is always brought in a different format. Curse of Strahd was a small scope adventure. Tales of the Yawning Portal was an adventure anthology. Mountain of the Mad Mage felt like both a resource for higher level play as well as 23 dungeons that you can pick and choose from for your own use. Perhaps if their flagship adventure is a FR-based module, then their "second adventure" will focus on Spelljammer / Planescape, or viceversa.
5. Two other game books will be published by Wizards of the Coast this year, but they will be developed by an outside team.
A part of me wants to say that these will be two renewed campaign settings, but it could very likely be an Eberron adventure as well as a Ravnica adventure. Maybe 2020 will be when another setting gets revived.
P.S. Dyson Logos' maps worked for Dragon Heist but I really hope we get back to detailed maps (Like Mike Schley's).
Edit: I'd rather see a videogame that is closer to Capcom's Dungeons and Dragons: Tower of Doom or Shadow over Mystara than an RPG. Something easier to pick up and play among friends.