First off, welcome to a slightly different way of doing things 
Fedora CoreOS has update streams and they all progress over time. Systems with updates enabled will move to newer versions. The only way to stay on Fedora 33 forever is to disable updates.
Though I think what you’re trying to ask for is
- how do I tell my current
next system to transition to testing or stable once f33 is in those streams?
Is that correct? Currently we don’t have a way to do that but I have discussed it with @lucab a while ago. Though I will let you know that we won’t be moving to F34 in next for 5 or 6 months.
Regarding rawhide, we do have an open ticket to create a rawhide stream, but that would mostly be for testing/development. I highly doubt we would expose it to end users as one of our production streams.