From a Reddit Question and Answer with Greg Boyd:
How can the Open Theist God promise every knee will bow, and every tongue shall confess Jesus is Lord, without compromising anyone’s free will?
How can a Calvinist affirm this without being a universalist? Look, this is an equally challenging passage for everyone who isn’t a universalist. For my two cents, I’m inclined to see this passage as expressing God’s loving bear hug around all humanity with the hope that all will come in. Yet, because love must be chosen, people always have the freedom to say NO THANKS.