It feels more like it's meant to be a tongue-in-cheek scene.
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It's a scene of 3 people that look/talk/act like Eren, Mikasa, Armin, 100 years after the end of the Titans, seeing a movie in a modern looking city about the events of the series.
It feels like a happy ending, but I'm pretty sure it takes place in the middle of the montage that takes place at during the ending credits. So it's actually kind of a downer considering what happens after.