Update: Ubisoft hasn't answered my inquiry, but it did drop this on Twitter, confirming that Assassin's Creed: Odyssey will be officially announced at E3.
See you at E3! pic.twitter.com/03NTPhCkCfMay 31, 2018
It's a very "This is Sparta!" moment, isn't it? We'll find out more in a couple of weeks: Ubisoft's E3 press event is slated for 1 pm PT/4 pm ET on June 11.
A rumor surfaced in March on Comicbook.com indicating that the next Assassin's Creed game will be set in ancient Greece. "Several sources" said it was so, although the site advised approaching the story with all appropriate caution; but it also noted that "murmurs" of a possible Greek setting had previously come up earlier in the development of Assassin's Creed: Origins.
French gaming site JeuxVideo added weight to that story today, and also a possible title, with an image of an Assassin's Creed: Odyssey "collectible helmet keychain." The helmet is very clearly in the Greek style, and the Odyssey is a famed epic about the Greek hero Odysseus, who takes the long way home after the Trojan War. That could make the Assassin's Creed timeline a bit hinky—Ptolemaic Egypt, the setting for Origins, didn't come into being until nearly a millennium after the Trojan War—but it's also possible that "Odyssey" isn't a specific reference to the poem as it is a cool word that very loosely fits the motif.
It's strictly a rumor at this point, but two consecutive, consistent reports—not to mention the fact that ancient Greece is obviously fertile soil for an Assassin's Creed game—makes it a reasonably solid one. The proximity of E3 lends weight to the report as well, as this is the time of year when surprises seem mostly likely to be blown. I've reached out to Ubisoft to inquire about the title, and absolutely do not expect a response—but if I get one, I'll let you know.