People started talking about the release of new hardware ahead of the OLED reveal, but there wasn't anything close to an "open secret" about its reveal timing. Few people had anything to say on that front, apart from some initial speculation that it might happen before E3. It was also mixed up with "Switch Pro" stuff that turned out to be wrong (such as M+R2). The Lite on the other hand had no chatter at all before its reveal. Its existence was reported on earlier in the year by Bloomberg and confirmed with a photo leak, but nobody called out a July announcement before it happened.
I would say we're in a pretty similar situation now. Bloomberg reported on it some time back, its existence is known to several people, but no one can speak to the announcement timing because Nintendo can hold that as close to the chest as they need to.