We've wanted to make this change for the last 18 months, but needed our Enterprise business to be big enough to enable the free use of GitHub by the rest of the world. I'm happy to say that it's grown dramatically in the last year, and so we're able to make GitHub free for teams that don't need Enterprise features.
We also retained our Team pricing plan for people who need email support (and a couple of other features like code owners).
In general we think that every developer on earth should be able to use GitHub for their work, and so it is great to remove price as a barrier.
A full FAQ on pricing is available here: https://help.github.com/en/github/getting-started-with-githu...
Hope that's helpful!
"Your account can not be downgraded yet because one or more of your private repositories is over the collaborator limit for the free plan. Please make sure that each of the private repositories owned by your account below has 3 or fewer collaborators before downgrading your account. Questions? Please contact support@github.com."
Am I missing something or is this not implemented yet?