At the end of Deadpool's recent, aborted attempt to kill Sabretooth, Magneto was preparing to kill Deadpool, only to be stopped by Sabretooth mentioning Deadpool's daughter is a mutant (something Wade did not know, fyi). But once he's free, as Mags mentions never expecting to have a reason to keep Wade alive (namely, to be a protective father of possibly one of the last mutants), Wade grabs Magneto by the shoulders and says he has one more reason.
I thought, given the aggressiveness with which he grabbed Mags, and Magneto's surprised expression, Wade was about to knee him in the groin. Not sure how that was going to qualify as a reason not to kill him, but I expected there would be some joke in there. But no, Wade whispers something to him, Magneto is surprised, says he'll hold Deadpool to his word, then leaves.
The question is raised, what did Deadpool tell him?
I know Gerry Duggan is also writing Uncanny Avengers, and the Red Skull, still possessing telepathic abilities from Xavier's brain (or something) is moving around in the background, doing stuff. And just from bits I've seen posted online, it seems as though Deadpool might know something's up*. Which would make sense, as it's been long established Deadpool's brain is pretty resistant to telepathic jiggery-pokery. And given Magneto hates the Red Skull, what with the Skull being a huge Nazi, and having Erik's best buddy's brain or whatever, Deadpool might have mentioned he knows the Skull's around and up to something, and he's going to take care of it.
Part of me thinks it's something much more absurd, except this is Magneto we're talking about. He doesn't really have a sense of humor, at least not the kind of one that would appreciate Deadpool's. But it could be something else, so if you have an idea, let's hear it. 'Cause I'm just guessing here, as usual.
* The Skull was able to deceive Rogue by appearing to be Gambit, though she's had enough training to, on a subconscious level at least, realize something is off. And the Skull was able to hide himself from Quicksilver when he went to check the old Avengers Mansion vault on the suggestion of, you guessed it, Deadpool!