This is a very tough question... This is mostly due to time overlap. This is where shit really gets confusing. As soon as Natsu destroys the Eclipse gate, everything should go back to how it was given that Future Rogue and Future Lucy never arrived. Which would completely destroy the normal timeline and replace it with the one below:
FT Goes to GMG
FT Wins GMG in the same way
FT goes home.
Which means that the whole thing shouldn't have happened. And here's where you get limbo! What the fuck happens to this whole slice of time from when Lucy gets caught to when Natsu destroys the eclipse gate? The thing is, is that the entire eclipse gate is what causes Lucy to be captured, it's what causes the dragons to come out, and it's what causes all the destruction. If you eliminate the Eclipse gate at any time between the start of the tournament and in the future when Rogue comes back, you're going to completely erase the entire timeline. If Rogue doesn't go through the gate, nothing happens. So if the gate is destroyed before Rogue can go through, how does the whole affair with the dragons occur? It doesn't. But if the whole affair of the dragons didn't occur, then how did the gate get destroyed by Natsu? It wouldn't have...
You have this infinite loop. And it makes no sense! Neither solution makes sense...
Future A: If the dragons occur and Natsu destroys the gate, Rogue can't come back to the past. Which means that the dragons can't occur and Natsu can't destroy the gate!
Future B: If the dragons don't occur and Natsu doesn't destroy the gate, Rogue can come back to the past. Which means that he will ultimately make the dragons occur and Natsu will destroy the gate, putting them back into this endless cycle.
If anyone can explain this to me, that'd be great.