Earlier quoted context omitted.
That's not quite true though. The fact that most models are in practice non-deterministic has been a huge point of contention. And there's nothing inherently stopping labs from continuously fine-tuning the weights after every new invocation. It's just a difficult (not to mention expensive) software and ML problem.
It's not "not quite true", it's literally true because alternative architectures like RNNs and Mamba fully update their own internal states, whereas transformers only append to the context. RNNs and Mamaba do not update their weights, but you could hypothetically scale the internal state to be as big as Fable's and GPT 6's parameters.
It just has big technical and economic challenges. But I expect advances there. There have actually already been big advances, though done in bulk fashion (RLHF).