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.