The sneak peek showed August pointing Rumple's knife at Gold/Rumple. That could be his way to rid Rumple of his powers/curse, and for Bae to have his dad back.
If August is really Bea and he were to kill Rumple, not only would Bea become the next Dark One, but his dad would die. So, I don't think that's going to happen. Perhaps there is another way to rid Rumple of his powers that we don't yet know about ….
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