Borderlands 2 and Superhot are both excellent shooters, for very different reasons—one is a colourful FPS with a bajillion guns and cool enemies, the other is a more minimalist, focused affair that's all about timing and careful movement. A mod that combines the two should be out in the "next few days" and, from the trailer above, it looks like a brilliant mash-up.
Superhot's key mechanic is that time only moves when you move, and when transplanted into Borderlands 2 that means being able to jump over bullets in slow motion, dodge massive machine gun fire, and vault over enemies' heads before popping them in the back.
Borderlands 2's enemies can be bullet sponges, but here—just like Superhot—it's one shot, one kill. Even though that negates the game's core charm of constantly finding a bigger, better gun to play with, I think it'll be a good excuse to jump back in and muck about for a few hours. It's not shown in the trailer but, presumably, you'll die in one shot too.
The mod's creator Blacktavius said on Reddit that it'll be out over the next few days, and that you won't be able to play with a gamepad. Keep an eye on the Borderlands 2 subreddit to find out when it goes live.