[mtgowns]

Originally Posted by Kaijo

10,000 dragons, eh? Are they real? An illusion? Some result of magic? Perhaps they are coming to destroy the Eclipse gate, since they feel that magic is too dangerous to be allowed to exist.

I have a bit of a different theory...

Spoiler for idea:

It should be noted that Arcadios (sp?) carries a Jade Amulet, and the princess is known as the "Jade Princess" - which means they're somehow affiliated with dragons and likely sympathetic to them. They're the two main proponents of the Eclipse plan.

Their claim is that in order to defeat Zeref, he must be killed before he becomes immortal. However, a dead Zeref means Acnologia would've never come to be... meaning the "dragon genocide" would've never happened and dragons would still be dominant, very likely preying on humans (with the Jade Dragon noting they're no more than food to them). So in the given future, the very destruction might've been a result of the Eclipse plan - although future Lucy is understandably only fixated with changing the immediate outcome.

After speaking with future Lucy, Jellal notes that there's something "off" about her story; this could be it. Also, since Charles has already seen the castle's destruction and Lucy "singing", we're assured that those things will happen - but it could be in a completely different context (e.g. the castle is destroyed to end the Eclipse Plan, not by dragons).

I'm probably just overthinking it and Mashima will very likely bring new elements to the table, but just some food for thought.