While major new macOS versions were released in October or November for the past four years, there is a chance that macOS Sonoma could be released in September this year, based on how beta testing of the update is progressing.
As noted by @iSWUpdates on X, the seventh beta of macOS Sonoma seeded to developers last week has a build number ending in “a,” while the seventh beta of macOS Ventura had a build number ending in “f” last year. A build number ending with an earlier letter in the alphabet typically indicates that beta testing is closer to completion.
macOS Mojave was released in September back in 2018. The seventh beta of that update also had a build number ending in “a.”
Read more at MacRumors.com