In the interview here: http://www.sffworld.com/2014/03/brandon-sanderson-exclusive-interview/?utm_source=rss&utm_medium=rss&utm_campaign=brandon-sanderson-exclusive-interview the second question says:
"2. Will we learn more about the character currently known as Hoid in Words of Radiance? Yes, you will. Watch for a story told at a bar."
So here's an excerpt from the story Rock told at a bar of a man coming out of a pool in the mountains that the horneaters call holy:
"Like person,” Rock said. “Maybe Alethi, though skin was lighter. Very angular face. Handsome,perhaps. With white hair.” Sigzil looked up sharply. “White hair?” “Yes,” Rock said. “Not grey, like old man, but white—yet he is young man. He spoke with me on shore. Ha! Made mockery of my beard. Asked what year it was, by Horneater calendar. Thought my name was funny. Very powerful god.”
Speculation is that Hoid (it does describe him) was coming out of that pool, and that the pool is a shardpool. So maybe Hoid's worldhopping happens by going through shardpools????