I don't think the White Walkers are all bad. There was a quote from Bloodraven in ADWD about how magic died out when men came into the world, and they all had to go into hiding. The Others were probably the dominant species of Westeros originally, then the CotF came along, then the First Men, the Andals etc, and over time they've been pushed back to the Land of Always Winter and into myth and legend. They want to take Westeros back. So, they're still villains but they have logical reasons for what they're doing.
It's either going to be Jon or Bran who brings us to the White Walkers. GRRM has said we're going farther north in TWOW, and we'll be seeing a lot more of the Others, and since Jon and Bran are the only two viewpoint characters anywhere near them it has to be either of them. My money's on Bran, personally, but I think Jon will be involved with the White Walkers as well.