"I've never been asked to go back to Doctor Who so I wouldn't keep my hopes up for the other one and it's not up to me, but I think I would much rather go back to Doctor Who and see The Doctor but if they ask me to do it, of course, I'll do it. I would love to. But who knows if Jack is in that Who universe still."He went on further to talk about what he would want to do with the Twelfth Doctor.
"Well, first of all I think the introduction would be interesting because he'd look at him and go..."really? What's all this?" and take it from there. You know, it's not so much about what Jack's adventure would be. It's the adventure of the Doctor and the joy Jack would have following him and being part of all that again.
I would love to fight the Cybermen. I would love to go back and deal with the Daleks again because obviously his death by Dalek and rebirth by the TARDIS (or so we "think so") is what makes him immortal. But yeah, lets look into that side of it. And also, lets cross with River Song."
He also discussed his role on Arrow and a Supergirl crossover/musical. Watch the interview in the player below.