3. Wolverine's Adamantium Skeleton
Does the Wolverine in the past have the memories of his future self or did those go with Logan when his mind returned to the present day? The former option seems most likely, and with X-Men: Days Of Future Past ending with Wolverine in the custody of Stryker, him getting his Adamantium skeleton before X-Men: Apocalypse seemed like a sure thing. The big twist though was that Mystique was actually impersonating Stryker, and there's no way the sequel can't address this. Does she take the villain's place and start experimenting on mutants like Wolverine? If so, that would make her entire arc in X-Men: Days Of Future Past utterly pointless, but if she saves him from the clutches of Weapon X, how does Wolverine get his iconic metal claws? Will he be left with the bone versions permanently? This may be where X-Men: Apocalypse's titular villain comes in. After Magneto tore the Adamantium from Wolverine's bones in the comic books, it was Apocalypse who re-bonded the metal to his skeleton and brainwashed the hero into becoming one of his four Horsemen (Death). It's convoluted, but this will likely be how he gets those metal claws.