The consensus for some time has been that we are getting a new Anthropic model ahead of the IPO (and that's not all), so I think we can safely say this is 100%. There were some new developments today from @synthwavedd though, who says that new Sonnet, Opus, and Fable are all in stealth testing. In fact, if you are using Claude, it's possible that you are in an early test flight and using one of them right now. So we may be getting a triple release from Anthropic, not just one new model.