Edit 2/ Now Up on Nick.com,
http://at.nick.com/1BDhouq
Edit/ Korra is back on itunes, there is a Book 4 Season pass available to purchase
https://itunes.apple.com/us/tv-season/legend-korra-book-4-balance/id917393749
Book 4 is here, Amazon.com have K401 After All These Years available to purchase online. Just like the end of Book 4 Amazon seem to be getting the episodes many hours before Nick.com do.
Link - http://www.amazon.com/gp/product/B00NW2H7C2?ref_=atv_dp_season_select_s4
As for Nick.com, they will have the episode up at some stage no later than Noon EDT, I will update this post with the Nick.com link and how to access Nick.com out side of USA.
When you have watched the episode make sure to go onto our forums and discuss the episode with our community.
http://avatarthelastairbenderonline.com/groups/avatar-the-legend-of-korra/forum/topic/k401-after-all-these-years-spoiler-discussion/