Even if I don't end up starting a New Game+, I love knowing it's always an option.
I had expected the feature to be in The Witcher 3: Wild Hunt, which I still haven't even begun (I'm only now on inFamous: Second Son, as far as newer open-world games go), but it is at least planned. CD Projekt RED says it's currently working on adding New Game+ as "the final DLC."
When this releases, it'll be free. "It won't happen this week though -- we need a little bit more time to finish it."