I think you answered it yourself? It’s coming soon, so it is not available now, but soon.
It's been coming soon for a couple of months now, meanwhile Groq churns out a lot of other improvements, so to an outsider like me it looks like it's not terribly high on their list of priorities.
I'm really impressed by what (&how) they're doing and would like to pay for a higher rate limit, or failing that at least know if "soon" means "weeks" or "months" or "eventually".
I remember TravisCI did something similar back in the day, and then Circle and GitHub ate their lunch.
I've found Bedrock to be nice with pay-as-you-go, but they take a long time to adopt new models.
https://console.groq.com/settings/billing