Speaking to Doctor Who Magazine, 46-year-old John admitted that he is unsure whether he will ever be asked to play his character again.
Acknowledging his "surprise" at an offer to face off with Peter Capaldi’s Doctor, John remained hopeful for The Master's future.
John said: "You know what, I don’t know. I mean, I wouldn’t have thought in a million years that I’d be back [in 2017], yet here I am talking about it, so never say never.
"So you never know. This thing called Doctor Who is a machine that just sort of goes on its own. It’s got its own rules. And if they want you back, then great. I would definitely think about it."
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If they want you back, then great. I would definitely think about it
Although John hasn't confirmed any definite plans to return, he did admit that he "feels lucky" to have acted through two eras of the hit sci-fi show.
He continued: "Will they ask? I doubt it. But I don’t know. I mean, I’m very, very lucky to have worked with two Doctors. Two brilliant, brilliant actors. So if not, I will count myself blessed to have been asked back; to have played him these two times.
"That’s wonderful. And we shall see. Who knows? Yeah, never say never. That’s very true."
It comes as Doctor Who showrunner Steven Moffat revealed that he had plans in place for a major alternative ending to series 10 involving John's Master and Missy (played by Michelle Gomez).
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The 55-year-old was speaking on Doctor Who: The Fan Show where he announced his original ideas for the season finale included Missy announcing that she is pregnant.
Steven said: "We concocted this whole scheme that I'd cliffhanger out of my era on Doctor Who, handing over to Chris [Chibnall] with Missy telling the Master and the Doctor that she's pregnant.
"I decided not to do that. Over to you, Chibs. Sort that one out, mate. Off you go. There we go.
"I think it was [a step too far]. It was only email lunacy. I don't know. I think the Master and Missy… I'm not quite sure about their flirtation and whether it's just showing off."