Joss Whedon on Why Loki Was Cut From AVENGERS: AGE OF ULTRON
I don't know if you remember this or not, but back in November of last year Idris Elba said that Loki was going to be in Avengers: Age of Ultron. Well, if you've seen the movie, then you know that he's not in it. He was originally supposed to be, but Joss Whedon ended up cutting him out, and in an interview with MTV the director explains why:
“Tom is not in the movie… Idris misspoke… twice. We did shoot something and it didn’t play. The movie has so much, is so filled and we didn’t want it to feel overstuffed. I really wanted to have Loki in it but I understood the decision, ‘Now there are too many voices in the chorus.’ At some point the embarrassment of riches is actually embarrassing.”
It would have been nice to see Loki return, but the movie does work without him, so if there was no need to include him in the story, then so be it. I'm sure that deleted scene will show up at some point, maybe with the release of the Blu-Ray/DVD. At this point it doesn't seem like we'll see Loki back on the big screen in the MCU until Thor: Ragnarok, which comes out on July 28th, 2017.