There was a big thread a while back (maybe a year and a half or more) where Rainman made a bunch of predictions about what will happen.
He theorized that John Snow is the bastard of Ned Stark and one of the Targaryen women. I cannot remember which one he said and I cannot seem to find the thread.
We all know Jon supposedly dies at the end of the last book. That was a shock to even me. I suspect either he didn't really die or he will resurrected somehow.
There's also Aegon Targaryen, Daenerys' nephew who we find out survived. He's a bit of a wild card.
I'd say it's impossible to guess what will happen at this point, especially with this writer.