The preview shows that Daenerys has at least one dragon flying with her army, seems the outcome is plainly obvious, unless the dragon(s)' are going to get a serious power gimp and/or the White Walkers have a power move they've been hiding.
Cos if cowardly Sam can slay one with a shard of dragon glass (obsidian) and Jon can fight one on almost even ground with a valyrian steel sword, a grown dragon should easily just lay waste to all of them with a single blast of dragon-fire while flying overhead.