No, LLMs have not plateaued, and each of the latest releases has been a proof of that.
Fable 5 is a model you instantly FEEL how smart and superior it is. GPT 5.6 Sol is a HUGE incremental improvement in multiple directions and dimensions.
DeepSeek v4 Flash 0731 is a huge improvement over the preview version, using exactly the same architecture.
Kimi K3 gets open weight models very, very close to the frontier.
No my friend, we are not done yet.