Is Natsu Dragneel "END" in the Fairy Tail anime adaptation? So I've heard/read that Natsu is END (Etherious Natsu Dragneel), but in the anime END doesn't get activated. In the manga we see that Zeref's reveals who he/it is, but not in the anime.

Is Zeref going to come back and awaken END (Because I'm sticking with the anime, not the manga)? Or is Natsu END even in the anime? (It could just be Hiiro not sticking with the manga?)
As was pointed out in the comments, they jumped ahead a bit on the reveal of Natsu's identity. Towards the end of the episode where Fairy Tail was disbanded, while Natsu is wandering off to go training...we cut over to Zeref telling Natsu to surpass him, and addresses him by his full name: Etherius Natsu Dragneel.

Per the Manga, We discover that Natsu is (probably) E.N.D. in Chapter 416, but it is fully and completely confirmed a few chapters later.

The anime went on hiatus as of Episode 277, which is adapted from Chapters 417 and 419...so if they followed the manga strictly, we wouldn't know yet. But, obviously, they wanted to pull that reveal before the series went on hiatus again.

So yes. Natsu is E.N.D.