Here's Joss's reply:
Watch his whole panel here (the director's cut answer is around the 2:30 mark):
It has always been my ambition never to do a director's cut of anything and always to make the movie with the studio that we both want to make. 'Ultron' was very complex and there was a lot of back-and-forth. My instinct is no. Just as an artist, I'm super f-cking lazy and that sounds like I'd have to go back, it would be hard. I don't think there's interest in it, right now. You'll see a bunch of stuff on the DVD in extras that were meant to be there, but, you know, the narrative came together very close to the way that I hoped that it would and I don't think it needs me to constantly tweak it. I feel you put something out and there it is."
Marvel Studios President Kevin Feige talked to Cinema Blend about Joss's original cut of "Age of Ultron" and seemed to agree with Joss about people not really wanting to see the footage they cut:
Not quite true. There are definitely fans who would love to see full director's cut versions, and not just deleted scenes or alternate endings. But we have to trust that the directors and studios know what they're doing in just sticking to theatrical versions with a crapload of other extras to sell those DVDs.
Most films you can put an assembly together and it can be two hours and 45 minutes to three hours. I think the longest version of this was two hours and 45 minutes, thereabout. The longest version of 'Ant-Man' was three hours, but nobody wants to see those versions of the movie."
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