Ubisoft has averaged a release of one game in the series every single year. This practice was halted after the release of Syndicate, and the studio delayed the release of Origins. After the release of Odyssey, there have been no further announcements about the future of the series.
The two newest games in the series, Origins and Odyssey, drastically altered the formula for Assassin's Creed. Many fans felt the series had become stagnant with very little mechanical change between titles. After a time, the quality of the games seemed to drop as more and more frightening and game breaking bugs emerged. After the poor sales and critical reception of Syndicate, Ubisoft decided to begin improving their game engines and the overall quality of the individual games. The two newest entries have incorporated more RPG elements, updated combat mechanics, and the ability to equip new armor and weapons. Their work seemed to pay off, as both Origins and Odyssey were positively received upon release.
Metro reports that several online retailers have allegedly leaked a game titled Assassin's Creed: Ragnarok before Ubisoft could announce it. They say allegedly because leaks like this aren't very difficult to fake, but considering that two separate websites had the same listing it could prove to be authentic. Apparently, there were two separate editions of the game, Valhalla and Mjolnir, which further add to the Norse mythology-inspired setting. Both postings were removed very quickly from their respective sites, so now there is little evidence to be examined.
Over the last year there have actually been several rumors to suggest the next game in the series will have a Norse mythology setting. One of the first rumors surrounds game would be announced in February. While these rumors may not prove the leaks, they do seem to lend them a little more credibility.
The MCU and God of War, so Ragnarok may be a successful venture for Ubisoft if the company decides to pursue it. It is quite apparent that Ubisoft is working on something new related to Assassin's Creed, but until something like Assassin's Creed: Ragnarok is announced officially all anyone has are best guesses and rumors.
Source: Metro