List all the villains that survived.
The purpose of this is that, in our minds, we know who can come back.
1) DIGIMON ADVENTURE: I think PIEDMON did. I mean, we don't really know what happens on the other side of the Gate of Destiny. There's also DATAMON, since ETEMON survived. And speaking of him, his GAZIMON assistants lost their memory but maybe they'll remember who they are.
2) DIGIMON 02: We know that DEEMON did. If the DIVERMONS traveled from the DigiWorld to that dark sea, how do we know he won't do the opposite?
3) DIGIMON TAMERS: D-REAPER. Seriously?! Making it go back to its primitive version? It can upgrade itself again!
4) DIGIMON FRONTIER: I don't remember any.
5) DIGIMON DATA SQUAD: I haven't seen it.
6) DIGIMON XROS WARS: I haven't seen it.
Did I miss anything?