[Lotrelf]

There's a saying, it says :"A life of sin ends in sorrow sooner or later." So, Sauron's sinful life had to come to an end. Sooner or later. This sooner would have been if Isildur had destroyed the Ring, and 'later' became when Frodo destroyed it. No, I don't think either of them would have run away. Gandalf a was Maia-a demi-god. It was his responsibility to do what he did. He would not have just fled. Valar would have another plan for that, but nothing of that happened so it's hard to say "what would have happened?"