I'm still thinking that the current Dragon Slayers are actually from 400 years in the past. OR, the slayers that participated in the games 400 years ago, were actually the current slayers.(Which would explain why the person in the mural fighting the dragon had Natsu's scarf on) There's a lot of complex stuff underlying all the time travel theories, and the time frame that we've followed until now, could be the alternate time frame. My head starts to overload when I think of all the possibilities. Once you throw time travel into the mix, then EVERYTHING that has happened before, could have been altered from the future. Meaning anything that may have seemed weird, or gone unexplained, could be explained now. I wonder if Mashima planned this since the beginning? If so, then there are likely many many clues that we missed.