User blog comment:B214/Question and Answers 6/@comment-185.112.105.215-20161218170008/@comment-9595671-20161221123950

Hmm... who knows, maybe they might just, it would be a surprise if they got a bit after the Ex Timeline's future and somehow do it, saving every inside and actually ending that beast or maybe heel-face turning it (the latter is likely a stretch) and a future better than the war currently in the EX timeline results.

For all we know, Ishibumi's gonna surprise us and is making us think they'll actually stay there for the 10,000 years, heck for all he know the Ex timeline will show up again in the main story for such a big twist because something else effects the time stream not by changing the past, but twisting the present and future.

I'll have to agree with Omega that EX itself is a wall that denies the possibilty. After all, until the series ends, anything can happen. I mean Ishibumi did say the characters are gonna get their happy ending, we just don't know how far that truly goes to and what twists are gonna be pulled.

Until the story ends, we can never say something can't happen, including a character dying. I know when I was reading Volume 12, Sieg actually dying actually surprised me cause the rest of his team mates didn't kick the bucket. Some characters originally didn't even intend to exist and Issei and Kiba were pretty much the same character.