ok so I found this on 4chan, so I don’t know how reliable it is, but apparently Isayama and Araki (the director of the anime) had a little interview. Someone posted a few translations but this one in particular piqued my interest;
Q: Who is the shingeki who left a deep impression?
Araki: Armin. Because he grows from weak to strong, but the strongness is not necessary a happy thing. Armin’s seiyuu was sad about it.
Isayama: We talked a lot about Armin’s growth.
Isayama: The story might not end with Armin being good friends with Eren.
Thoughts?? Although the development to that point would be rather interesting, I think it would be overall rather sad… I love the trio and it’s weird to imagine Armin and Eren not being best buds anymore…