If you count spin-offs, Assassin's Creed has had a new release every single year since the first game came out in 2007. If you don't, the series has only missed 2008 and 2016. That will change in 2019, as Ubisoft opts to skip a major release to take more time developing the next entry.
GameSpot reports that Ubisoft CEO Yves Guillemot spoke on the decision at Gamescom, saying that the back-to-back releases of Origins and Odyssey were enabled because the two games were in development simultaneously. As a result, Ubisoft's teams will need more time to create the next major entry in the franchise.
"On Assassin's, we had a game [in 2018] and we have one this year, but we are not going to have a full-fledged Assassin's next year," he said. "It's just because the team were working separately, so we have two games now, one year after the other. But next year you're not going to have a fully fledged one."
Officially, Ubisoft dropped its cycle of annual releases in an effort to reinvent the series ahead of Origins. However, Ubisoft still published two Assassin's Creed Chronicles games in 2016, India and Russia.
Guillemot confirmed that this time, there would not be any spin-off titles in 2019. Instead, the company is opting for continuous support of Assassin's Creed Odyssey throughout the year while it quietly works on its next project.
At E3 2018, Ubisoft EMEA executive director spoke to GamesIndustry.biz on Ubisoft's plans for those ongoing updates, referring to Assassin's Creed Odyssey as a "live service" with the promise of post-launch content "planned for a long time."