Doctor Who doesn’t return until April 15, but once again it’s facing a recurring existential question: Who will play the next Doctor when the rebooted series returns the following season?

There are growing calls that the new Doctor is played by a black or female actor, to better reflect our increasingly diverse society — not to mention the increasingly diverse audience now following the rebooted Doctor Who.

Diversity is not quite the divisive issue in the UK it is in the US, but it is an issue just the same. The UK is now one of the most diverse television audiences on the planet, not just in the urban centers of London, Manchester, and Birmingham but also — and increasingly — in the rural regions familiarized here by period dramas like Downton Abbey and Pride & Prejudice.

Doctor Who, available in virtually every British home on BBC, is not the cultural lightning rod in the US as it is in the UK, but it has attracted a loyal, devoted — and noisy — following on BBC America, where it has arguably become the cable outlet’s most important, high-profile recurring drama, along with Orphan Black. (Just try to imagine Orphan Black with a male lead, and you begin to see some of the issues confronting Doctor Who as its brain trust mulls over the idea of quite literally “going in a different direction.”)

Doctor Who’s ratings have tumbled of late across the UK, but BBC America’s more modest expectations have been exceeded. This past December’s Christmas special (right) broke a BBC America ratings record, with nearly 1.7 million viewers, nearly 900,000 of those in the coveted, hard-to-reach 18-49 and 25-54 age group. 

Just as importantly, the Christmas special was the most talked-about TV program on social media on Christmas night, according to Deadline.

In the UK, meanwhile, Who’s audience has dropped below 6 million some weeks, less than half its series-average of 12 million during the reboot’s early years.

The coming season marks the reboot’s 10th anniversary, but already four different actors have played the time-travel fantasy’s trippy hero, beginning with Christopher Eccleston in 2005. 

David Tennant (below right) followed, for three seasons, followed by Matt Smith, who stayed for another three. Peter Capaldi (top) will return for what will be his third and final tour through space and time when Doctor Who returns in April.

Capaldi announced his decision to leave last month while filming new episodes. (Production on the new season is ongoing and will end in late March.) Capaldi confirmed that this year’s Christmas special will mark his final appearance, and possibly the unveiling of the new Doctor, though it’s equally possible the mystery won’t be resolved until new episodes air the following year.

Capaldi made little effort to hide his annoyance over the BBC’s decision to move Doctor Who to a later time period on hyper-competitive Saturday nights, this past season in the UK. (One of the oddities of UK TV is that Saturday is the most-watched night of the TV week — and the most competitive, with hits like Great British Bake Off, The Voice, X-Factor and Strictly Come Dancing all vying for viewers.)

Doctor Who’s audience crosses all age boundaries, but it’s a family show at heart.

And nothing kills a family show faster than moving it to a later hour, Capaldi said. He has a point. Imagine how Once Upon a Time might do, for example, if ABC moved it to 10 p.m. Sundays, away from its family-friendly time period of 8.

Changing time periods is only part of the problem, of course.

There’s a sense among many Who followers that the trippy time fantasy has lost its way in recent seasons.

It always rode its luck on its goofy charm and affable nature, but there’s a growing feeling for some that it’s no longer as fun as it once was.

Certainly, the choice to follow the young, dashing Matt Smith (left) with the more studious, Shakespearean-trained Capaldi was a risk, but no more so than choosing then relative-unknown Smith to follow the popular and widely accepted David Tennant.

Capaldi’s impending departure, coupled with the series’ UK ratings slump, has fueled speculation that the new Doctor should be black, or female, or even both.

Doctor Who’s longevity — it first aired in 1963, after all — is owed to the inspired story twist that allows the Doctor to  “regenerate” his form every few years.

That’s made it possible for 12 different actors to play the role over the 36 seasons, spread over 53 years, that Doctor Who has been on the air. The new Doctor will be the 13th overall if you’re keeping track. Make of that what you will. 

Longtime followers have their favorite Doctors, of course; more than a few fans of a certain age say Doctor Who hasn’t been the same since Tom Baker hung up his cloak one final time in 1981.

The reboot, though, was always going to be different. And not just because it was nearly 40 years later — in 2005 — when playwright Russell T. Davies thought it would be “rather fun” to bring Doctor Who back to life in a hip, revitalized modern-day version that would reflect both modern times and modern-day social mores.

It’s that desire to reflect contemporary times that’s revived talk of changing the face of Doctor Who — literally.

Just as Idris Elba has been mentioned as a possible Bond replacement once Daniel Craig turns in the keys to his Aston Martin, David Harewood is one of the actors subject to online speculation that he may soon be fitted for time travel in the Tardis.

Doctor Who is headed for a sea change regardless of who’s cast as the new Doctor. 

Longtime showrunner Steven Moffat, who co-created the equally trippy Sherlock reboot with writing partner Mark Gatiss, has handed the reins to Broadchurch writer Chris Chibnall, who wrote some of Doctor Who’s more adventurous, action-driven episodes under Moffat’s tenure.

Talk that the new Doctor might be a woman has inevitably thrown the focus on Olivia Colman, so good in Broadchurch as hard-luck homicide detective Ellie Miller.

Chibnall and Colman have a history together. In Broadchurch, Colman played a workaholic and troubled mom torn between loyalty to her family and empathy for her best friend, whose young son has just been found murdered.

Colman appeared in Doctor Who once before, in the 2010 episode “The Eleventh Hour.”

Not to be outdone, Harewood, familiar to US viewers for his recurring role in the 2011 and ’12 seasons of Homeland as CIA deputy-director David Estes, also appeared in a Doctor Who episode, the 2009 Christmas special, The End of Time. 

That could be telling because that’s the episode in which Tennant’s Doctor passed and was regenerated in the form of Matt Smith.

This is not the first time Doctor Who and diversity have been mentioned in the same breath. Moffat recently admitted the role was offered once before to a black actor, but that “it didn’t work out,” for “various reasons.”

Interestingly, the Doctor’s companion will be played by UK dancer Pearl Mackie (left), who is herself black, being of West Indies descent.

Though it’s not Moffat’s place to say — not really, it’s Chibnall’s call — Moffat did say it would be “amazing” for Doctor Who to have two non-white leads.

Given everything that’s going on in the world right now, who does or doesn’t play the new Doctor may seem like a trivial pursuit. 

Doctor Who is escapism, however, and it’s always had a strong crossover appeal between the real and the imagined. As one prominent UK women’s rights campaigner said, it’s only right that the new Doctor be a woman, but that would only be truly emancipating if the Doctor’s assistant were a man.

Either way, Doctor Who is poised to make a potentially firm and decisive statement. Not every goofy, charming family show can say that.