Although it was rather obvious in hindsight, Assassin's Creed Infinity's announcement came as a big surprise to many. While individual games may play some role in the future of the franchise, it's also clear that its focus is in this live-service title. Ubisoft is likely hoping that this evolving world with multiple settings will keep Assassin's Creed fans' attention for the coming year, building and building upon an initial title and story.
However, what that is and how that works exactly has been left up in the air. It'll likely be years before fans know more, but the thing is, the franchise is and has always been interconnected. Assassin's Creed Infinity can't ignore Valhalla, as many plot points remain unresolved, and some are unlikely to do so during DLC. For example, perhaps playable Basim in AC Valhalla will only last through DLC, or perhaps that somehow translates over to Infinity. That's questionable, but one thing DLC is unlikely to resolve may very well serve as the premise of AC Infinity.
Assassin's Creed Valhalla's Ending
Assassin's Creed Valhalla's entire story was split between various sagas that told smaller but connected stories, and perhaps format-wise, AC Infinity could work in a similar way. Each "saga" of sorts could be its own contained story that is replayable, has multiplayer, and is a good sandbox for parkour. But the game has to explain how Assassins across multiple settings in Assassin's Creed Infinity are able to travel, get around, and accomplish some form of globalized goal. With that in mind, Valhalla has multiple endings of sorts, but the modern-day one may set it up perfectly.
Layla, through Basim and Aletheia's machinations, ends up with The Reader (who is truly Desmond). Since The Reader and Layla are caught in the Grey, they are trying to find a timeline wherein the next big catastrophe never happens. Indeed, the Isu failed to stop the First Catatstrophe despite developing seven different plans, with the seventh leading to the events of Assassin's Creed Valhalla. Desmond was able to stop the second in AC3, but ever since then, the world has been moving toward yet another catastrophe. Every moment and decision has played into this, with Layla offering Desmond a fresh perspective into looking for answers.
Assassin's Creed Infinity's Never-Ending
As The Reader looks for a timeline where there is no future Catastrophe to wipe out humankind, Layla suggests to look further back at other timelines: not the here when Layla saves the world, but to go back further to when Desmond did. This, in turn, could serve as a plot point by which to explain AC Infinity's storyline and give the live-service title a unifying purpose: preventing the next catastrophe. With Desmond and Layla operating within the Grey, perhaps they will be able to reach out through the timelines and manipulate certain points, as the Isu have also done. The Isu reached forward, but it makes sense that Desmond and Layla could go back.
Manipulating historical events, sometimes in smaller forms than others, via the Assassin vs. Templar conflict would resolve a lot of questions about how the game could work, and give a simple enough structure that hopefully those who prefer traditional single-player will still find something to enjoy in the new direction. It makes sense, of course, but this is mostly speculation. AC Infinity, at the end of the day, can't ignore the events of AC Valhalla, but what direction Ubisoft takes from there is anyone's guess.
Assassin's Creed Infinity is in development.