How about we go through the list and see the things that hints that either Amon IS Aang, or is VERY connected with him:
- The way Aang used spirit-bending with his thumb and fingers against the forehead is exactly the way Amon does it.
- Was that a spiral of air/smoke around Amon when he jumped to go after Korra after she broke out of her box?
- The preview actually showed Aang's statue with Amon's mask on it. I don't know if that was just the Equalists being ironic, or some kind of hint.
- Aang and Amon are the only two people ever shown to "walk out" of a bloobend.
Maybe Aang's middle child that got twisted due to his father's death? I mean, Aang likely didn't die of natural causes, since according to what I've read, Aang died when he was around 66.