I'm barely into the first book, about in the middle of the second episode for comparison. But im predicting the white walkers(which are called "the others" in the books) will become more prevalent once winter does indeed come. But thats just a prediction and since we were introduced to all the main characters(i think) so far, and it will be in jon snows perspective and his encounter with them. Since he just joined the black so I could see it happening by the end of the season