I agree that for average web dev tasks the open models are already good enough. I've had good experiences with both DeepSeek and GLM. And these models are just better for anything security related since they don't throw massive hissy fits.

However I do actually have a project where I need the frontier models--I'm working on a deep learning project of moderate complexity (something novel/state of the art within its domain, adapting a known approach from published research in a related domain). The difference from Opus 5 -> Opus 5.5 was huge for my project. Opus 5 was struggling, Opus 5.5 is doing really well.

I think the demand for frontier models will continue to be there, at least for a subset of tasks, although I agree that it is probably going to shrink as the non-frontier becomes more and more capable.