Re: From Sir Humphrey's Playbook
You can never rule out future changes to any law. However, the hurdles here are, as you point out, pretty high: a change like this would require unanimity amongst EU members. And, as things stand, would have to be vetoed by Germany at least where the constitutional court has already stated that it's unconstitutional and thus Germany would not be able to ratify the law.
Getting the ECHR amended would be even harder…