Thanks to the mid-credits stinger attached to Deadpool, we know that Cable is coming to the sequel. We also know that Deadpool himself specifically thinks that Dolph Lundgren could be a good fit for the part (though he did also mention Kiera Knightley).
Clearly, one of Lundgren's people passed the news on, because despite professing himself not to be a comic book fan, he does know about the upcoming role, and he too suggests he'd be a good fit.
Talking to Nerdist, Lundgren was asked if he ever saw himself returning to the genre after his take on Punisher in 1989 was a bust (it's actually a great little cult gem):
"Thats a good question. I havent watched a lot of these superhero movies; for some reason, I dont know, Im just busy making films. I did hear in Deadpool, isnt there a character named Cable thats coming? Like, hes a big guy? I guess I could kick some butt doing that, I suppose. Well see. When I saw the picture, he looks a little bit like Ivan Drago mixed with Gunner Jensen mixed with I dont know."
He certainly still look the part, even if he's probably a touch on the old side. And there's absolutely no doubt that he'd cut a hell of a figure in Cable's iconic outfit. The only real issue is that despite his lengthy career acting in films as an actor, he's not actually all that great at acting.
Maybe don't tell him that though.