The Avengers: Age Of Ultron is now available on Netflix through Canada.
It's currently not available in the U.S. as of yet, but may be this Summer.
No worries though if you don't reside in Canada as Ultron has you covered: You can use the Chrome Browser and the Hola extension to access it (obviously use at your own risk).
There is also a program called Smartflix.io, which can access Netflix content through different countries (again: use at your own risk).
In addition, if you live close enough, you can probably just cross the border.