[a9dhalaan]

I think the main reason is they tried training a heavy weight model that was supposed to be opus 3.5, but it didn't yield large enough improvements to 3.5 sonnet to justify them releasing it. (They had it on their page for a while that opus was coming soon, and now they've scrapped that.)

This theory is consistent with the other two top players, Open AI and Google, they both were expected to release a heavy model, but instead have just released multiple medium and small tier models. It's been so long since google released gemini ultimate 1.0 (the naming clearly implying that they were planning on upgrading it to 1.5 like they did with Pro)

Not seeing anyone release a heavyweight model, but at the same time releasing many small and medium sized models makes me think that improving models will be much more complicated than scaling it with more compute, and that there likely are diminishing returns with that regard.