No, the keys themselves are fine, and are not going to be "disallowed". Its the SHA-1 part of the signature algorithm that is the problem. Fortunately you can use SHA-2 with your existing "ssh-rsa" keys, as the release notes clearly say:
> The better alternatives include:
> The RFC8332 RSA SHA-2 signature algorithms rsa-sha2-256/512. These algorithms have the advantage of using the same key type as "ssh-rsa" but use the safe SHA-2 hash algorithms. These have been supported since OpenSSH 7.2 and are already used by default if the client and server support them.
> The better alternatives include:
> The RFC8332 RSA SHA-2 signature algorithms rsa-sha2-256/512. These algorithms have the advantage of using the same key type as "ssh-rsa" but use the safe SHA-2 hash algorithms. These have been supported since OpenSSH 7.2 and are already used by default if the client and server support them.