I don't think there is a need to rush a release but:

• the next release contains API breaks: we should build a good changelog
• we should make a conscious decision on what is a release blocker

For the changelog, I think the commit messages from python-tuf PR theupdateframework/python-tuf#2165 are probably a good start for documenting the signer API changes

As release blocker proposals:

• Add Google Cloud KMS signing capability #442, Add HSMSigner #472 Signer implementations would be good to have to verify the signer API design
• Design key import/generation for the signer API #466 I don't think private key generation/import/storage needs to be fully implemented, but we should have the story ready
• signer API: review exceptions #468 likewise, at least a high level description of "this is how exceptions should work in signer API, and this is the current situation" would be helpful