Hypothetical Twilight question: For devout fans only?

That's a hard one. We already know what he would do if Bella died but we don't know if he would go to that extreme over his family. Would he let his true love die and then kill himself, or would he save her and let the people who have been his family for centuries die? I think he would go with the first. He would let Bella die and then kill himself, in my opinion.