I agree as well - I'd like to know why all of sudden, now, the Night King is moving on the humans.
Keith, I think he was just waiting for the right season... the final one. Winter does equate beautifully with the death of things, hell freezing over and the transition to spring and new life classically and like all good mythology Thrones refers back to traditional archetypes and symbols very respectfully.
It was good to see a return to the story delivering some very memorable moments in this season finale as well. Interesting to see Arya go public as assassin and assume her power and her adulthood. Little finger's end was a moment of magical tension more like some of the earlier seasons greater moments like Ned Stark's execution... tho the red wedding and Dani's transformation bringing the dragons back through fire are going to be hard peaks to top.