The shot starts hovering over a post apocalyptic wasteland. A ruined, silent and black city rots while a collection of quit coffin-shaped air crafts cruise in the atmosphere. They are looking for something. The coffins up and and deploy an army of folded up Sentinels.
The camera moves down, past the wrecked building, underground and into a secret bunker. Inside a gaggle of future mutants ready themselves for the oncoming assault. Iceman, Warpath, Sunspot, Bishop, Kitty Pryde, Colossus, and Blink are ready. Rumblings from above start, the Sentinels are drilling. A drill breaks through, they scatter. They're preparing for something.
Blink opens her first wormhole, it's pink. She jumps from wormhole to wormhole alerting the others. She yells, "Time's up." Sunspot heats up, and he looks great. Kitty Pryde grabs Bishop's hand and the two take off. The camera follows them, and clearly it's up to the others to protect whatever it is Bishop and Kitty Pryde are up to. They run through the walls and racks of provisions. Iceman appears, riding his majestic ice slide through the hallways, ready to fight. Kitty Pryde passes Iceman, they share a knowing look — and it's most likely a goodbye. Farewell to the only characters we have an emotional connection with because you had screen time! Time is running out because the Sentinels are already inside.
The giant monsters creek in. They look 100% like the new fangled Gort from The Day The Earth Stood still. Like furry, metal monsters. And they can do ANYTHING. Literally anything — it's almost too easy and it kind of feels like cheating. But that's kind of the point because this terrible mutant future is supposed to be so bleak, and such a no-win situation that the only option is to go back to the past and prevent this future. An ethically dangerous dilemma, but necessary when everyone is dead. The Sentinels begin to fight, and here's how it goes down. (Spoiler alert: Not well for the mutants.)
Colossus goes full metal and takes on a Sentinel. The robot rips off his arm. And later STOMPS ON HIS HEAD. Colossus is dead.
Another Sentinel chokes Sunspot out. He tries to melt the sentinel but the thing just adapts, the Sentinel freezes himself to counter balance the heat. Sunspot is choked to death.
The exact opposite happens to Iceman. The Sentinel heats up and rips off his head.
Another Sentinel opens up its face and melts Warpath to bits with a laser blast.
And Blink is impaled by a giant Sentinel arm.
Meanwhile Kitty Pryde and Bishop are locked away in a safe. Kitty is blasting white light from her hands into Bishop's brain. The Sentinels break in melting away the giant safe door. Kitty looks up and says, "Too late, ********."
And then Kitty and Bishop disappear — presumably into the past, because everything resets. The bed in the safe is gone, the provisions evaporate. Were the lives of our mutant buddies spared as well? Most likely. Sounds like Kitty Pryde was practicing her newly acquired time travel skills on Bishop, before she goes way far back with Wolverine.