The Wayback Machine came back long enough for me to snap this screenshot, confirming that Claude 3.5 Opus was listed as "Later this year" on Anthropic's models page a few weeks ago but is no longer mentioned at all
https://web.archive.org/web/20240930124545/https://docs.anthropic.com/en/docs/about-claude/models compared to https://docs.anthropic.com/en/docs/about-claude/models
Blogged a bit about this here https://simonwillison.net/2024/Oct/22/opus/