Even if models stopped improving now, I would use them. They provide so much convenience, I'll never go back. There's no need to keep changing.

In fact I'm more or less at the point where I don't even want the model to get better, I care more that it outputs faster.

We're on said plateau. In terms of normal coding usage, models have not become wildly more useful in the last few months. The existing open models that are useful today will remain useful.

For coding in existing languages? Probably indefinitely. And huge swathes of human civilization run on decades-old codebases.