I don't even know whats going on anymore
so we thrown some kinda possible timeline and then uh back to where we were for some reason.
Who even knows.
Maybe the author was going to go a completely different direction with the story, but changed their mind and decided to go back on that, just writing it off by use of Mephisto as a possible future.
That said, something will have to change in order to prevent that future from happening. It's possible Mephisto could personally involve himself for the sake of preventing it, but that doesn't seem his style, with him always using others to accomplish his goals instead. Who knows, maybe they'll do something along the lines of X-Men Days of Future Past, with Mephisto having Paku either sent back in time, or at least just her mind to her younger self, and use her to warn everyone of the future that is to come, with that allowing things to change.