Does that means if by any chance all frontier model companies agrees to use an open protocol for the API open router would go out of business?
It's more complicated than that. Lots of providers use an "OpenAI-ish" API, but many of them have subtle differences in things like tool calling or thinking blocks. OpenRouter normalizes the wire format.
OpenRouter does more than just proxying; they also aggregate providers for open-weight models, which has a stabilizing effect on pricing and gives you protection against a single provider's downtime.
no. i don't know if openrouter even guarantees consistent protocl across models.
the value of openrouter is it offers centralized billing. you can route your calls to any provider you want, test a whole bunch of models against each other, and you just get one bill from openrouter. switching to a new model, or a new provider of the same model, doesn't mean setting up a new billing account with a new provider.
All the model companies except kind of Anthropic (and even they half-assedly do) implement the OpenAI API. It's not an open standard but, like the S3 API, it effectively is.
And, to answer your question, no. The existence of a common API makes it trivial to change zero code and send requests to a different model.