I guess that is what will happen when no one is truly care/love Harry and Severus? Because if they are, even Voldemort still in Harry, there might be some way to destroy Voldemort or lock him. But Severus' anger and bitterness accidentally (I think) break the lock (Harry's soul) that seal Voldemort, so I this sad ending for them is unavoidable...
Thank you, this is a great fic, just feels sad that no one care or able to save Harry and Severus.