We're two years away from the 40th anniversary of Crisis On Infinite Earths. DC has already destroyed the surviving characters from COIE (literally in some cases and just character in others) and Dark Crisis. They've also brought back the "Infinite Earths" twice now, if we count Convergence.
What's left for DC to do for the big 40th? Will we see another reset/reboot or will the pre-COIE Multiverse get its own titles in 2025. Will they bring Harbinger back and use her as a villain for a new Crisis?
I think the best thing they could do is launch a new Multiverse: Multiverse 2025.
Multiverse-1956: The pre-COIE Multiverse
Universe-1986: The post-COIE Universe
Multiverse 2005: The post-Infinite Crisis Multiverse
Multiverse 2011: The post-New 52 Multiverse
Multiverse 2023: The post-Dark Crisis Multiverse
Multiverse 2025: A New Beginning
This new Multiverse would launch with all new #1s and everyone starts from day one. For the first year or so, no sidekicks, no teams, limited crossovers as each character starts over completely. Books are published on several Earths/universes.
Earth-Zero: "Ultimate DC," ground-level reboot.
Earth-One: "Classic DCU," iconic versions of DC characters in books that are light on continuity.
Earth-Two: "Golden Age Earth," two books set in the 30s and 40s: JSA and World's Finest.
Earth-Three: "Syndicate Earth," with "Syndicate" and "The Adventures of Lex Luthor" the only two titles.
Earth-Four: Ground-level reboot of the Charlton characters, with Blue Beetle and Peacemaker titles at first.
Earth-Five: Ground level reboot of the Marvel Family, though now known as the Thunder Family. One title to start: Captain Thunder.
Earth-Six: Horror/thriller universe, with Swamp Thing and Hellblazer titles.
Earth-Seven: Sci-fi Earth, with a Challengers of The Unknown title reimagining the team in a sort of "Star Trek" format.
Earth 10: Earth where Nazis one WWII and the Freedom fighters fight on. Mini-series or one-shots.