iOS 17 will almost certainly be unveiled at the WWDC (WorldWide Developer’s Conference) in June. That’s Apple’s annual developer conference, which is typically focused on software but occasionally includes new hardware. We say “most likely” for WWDC because there is always the possibility that it will be announced sooner or later. Since iPhoneOS, Apple has always announced the new version of iOS at WWDC.
Apple will announce iOS 17 along with a slew of new features that will be included in the update. On the same day, the first developer beta was released. The public beta is usually released a month or two later.