The Winds of Winter can only really be considered semi-canon at this point. For the simple reason that it hasn't been released yet. Here's a breakdown of canon rankings basically..
1st: A Song of Ice and Fire published novels
2nd: Prequel novels
3rd: World of Ice and Fire book
4th: Unpublished novels
5th: TV Show
With that said, it's perfectly safe to use info from the winds of winter for now :p