The following video contains slight spoilers for X-Men: Apocalypse, sets up Wolverine 3 and possibly the Gambit solo movie. You have been warned...
The post-credits scene in X-Men: Apocalypse takes us back to the Weapon X facility where Jean Grey, Cyclops and Nightcrawler were being held and it's also where Wolverine’s skeleton was bonded with adamantium. Just like in the original movies, this was overseen by William Stryker, but in this new timeline, Logan was freed from his cell and unleashed on Sryker’s soldiers. A mysterious figure in this final scene has to step over the bodies left during Wolverine’s escape, but that doesn’t deter him. He soon finds what he’s looking for: a vial of Wolverine’s blood marked "Weapon X." Satisfied with finding his prize, he sticks the vial in a briefcase labeled "ESSEX CORP." The name might be new to the X-Men movie universe, but hardcore X-Men fans know that the briefcase refers to Nathaniel Essex, a.k.a. Mister Sinister.