It's possible that they've determined that Opus no longer makes sense if they're able to focus on continuously optimising Sonnet. That said, Anthropic have been relatively good at setting and managing expectations, so today would have been a good time to make that clear.
Internet Archive confirms that on the 8th of October that page listed 3.5 Opus as coming "Later this year" https://web.archive.org/web/20241008222204/https://docs.anth...
The fact that it's no longer listed suggests that its release has at least been delayed for an unpredictable amount of time, or maybe even cancelled.