The basic versions of every iteration of regular Civ were all released in October except for the original Sid Meier's Civilization and Civilization V, which were both released in September.
As of this Friday, it is 6 months to September, 7 months to October: near perfect timing for a PreRelease marketing blitz culminating in either month. On the other hand, waiting until May to announce officially gives only 4 months to September, 5 months to October - shorter than the usual PreRelease marketing campaign.
No telling for certain, of course, but I would be very surprised, assuming a 2024 release for Civ VII, if we don't hear some kind of Teaser at least by April - perhaps a Double Fake April Fool's announcement to send us all into spasms of speculation . . .