CentOS will be useless as a replacement for RHEL. Without the guarantee of binary compatibility, any CentOS Stream update may break your locally installed applications.
And I only recall CentOS significantly trailing RHEL at the major version updates (e.g. 6 and 7). Other updates seem pretty timely, and the major version lag doesn't leave me vulnerable.
I can see this being useful for developers who are building something that needs to be compatible with the next major release of RHEL, but I'm not sure who else it will be useful for.