I'm new to this site. Forgive me if I make some mistakes. Please inform me if I do so I don't cause offense to anyone, break rules, or such.
It seems like a lot of these theories are complex and well thought out. So much in fact that you guys have my brain melting!
I'm just thinking, what if the situation was not complex to that(-your guys's in depth theories) extent? Maybe someone has mentioned this one already so, again, forgive me. What if the two timeline paradoxes you guys were talking about (future1 and future2) were actually one in the same?
Say Future Lucy and Future Rogue are from the same timeline. On the seventh (or whatever the exact date was) Future Lucy wakes up in wreckage only to find her friends dead and a dragon apocalypse upon the world. So she panics and uses the Eclipse Gate to go to the past and warn them. By doing that, maybe she unintentionally closed the Eclipse Gate. Seven years later, when the Gate had enough magic to open again, Future Rogue uses the Gate to travel back and carry out his said plan of killing Lucy (who closed the Gate) and using the Eclipse's magic as a magical cannon to kill the dragons. As for how the dragons came maybe that's the second timeline? ...This goes beyond my brains level of functioning.
It does seem as though Future Rogue considered the possibility of it being closed by her unintentionally, but maybe he didn't realize it was closed by her going back in time. He seems to be one of those believers in the 'everything happens for a pre-planned reason' theory rather than the confussling theory of there being multiple paradoxes's. Hiro Mashima's Rave used the 'Fate theory' so it might go like that again, but I guess that's how Future Rogue justifies killing Lucy.
Again, sorry if someone has already claimed this theory. I am by no means trying to steal your glory.