Was there any reason given why the WW's are that interested in newborns? They can pretty much take what they want and evidently cannot procreate - but what are they doing with the newborns to leverage not killing everyone?White walkers take winterfell and march to king's landing. They win and are about to kill cersei and what is left when she offers her newborn as a sacrifice (i e. Craster). White walkers then retreat north. Not likely, but just a thought.
I would have said maybe john/danny love child but that would take to long with number of episodes left