Mr Selfridge's creator Andrew Davies has said that he always planned the show to be just four series long.
Andrew is behind the ITV hit period drama and told Digital Spy that fans may not get to see it run for longer than four series if he sticks to the original plan.
He said: "It was always conceived of as four series - that is, if people liked it enough. People seem to love it, so I think we can do the four series."
Andrew added that Harry Selfridge, played by Jeremy Piven, would take a different turn in the upcoming third series which is currently filming, after his wife dies.
He explained: "He was just such a good boy all through the second series - I'd like him to cut loose in the third.
"[In real life] he became increasingly wild and reckless and finished up penniless - so it's got a tragic arc at the end. I guess we're going to stick to that."