I think they are really planning for a third single. They are aware that Unbroken would be a hit and preparing it to be the last single of the era. They wan't to end the era with the biggest hit Demi could have. But as much as possible ANL should be released as 3rd single and Unbroken as 4th.
But Unbroken would be a much better single choice.
I'm not sure. It could make her to a electropop girl, if it gets her first huge hit. I don't want that, it would suck to see her doing that generic music ONLY.