User blog comment:EvanDude345rv5/Fairy Tail 335 : RIP Ultear/@comment-5782007-20130616032455/@comment-1359322-20130616042537

http://i25.mangareader.net/fairy-tail/333/fairy-tail-4200003.jpg

After reading this again i realized that Mashima actually placed the 10,000 Dragons as the "first" future and "Acnologia" as second future. Since Zirconis said Acnologia bathed in Dragon blood to become what he is today maybe his existence disappeared in the first future since he failed to become the Dragon King, while in the second future Acnologia killed those Dragons and become Dragon King. So in this "third" timeline, Acnologia killed the remaining 9,993 Dragons and became Dragon King as well.

Now here's what hit me, Mashima created Acnologia in a way as Zeref said a being that can't be opposed, and if he wants Acnologia to be defeated then he'll have to create a weakness for Acnologia, so he'll use the 7 Dragons as a reason to why Acnologia failed to become "complete" sort of thing and use this as a plot to defeat Acnologia.