Billie Piper and David Tennant told fans at LA Comic Con that they would love to return for a possible movie:
While reuniting at LA Comic Con recently, Piper and Tennant were asked if they'd consider starring in a Doctor Who movie, to which Piper immediately answered: "Yes," with Tennant adding, "Sure!"
"I always was pitching for that," Piper continued. "Where's the film?"
"Where's the movie?!" asked Tennant.
"And we're the ones." Piper laughed. "I loved it that people went to see the last Doctor Who episode in the cinema. I just loved that. I would love the Doctor Who experience on the big screen. They're sort of like films anyway. But yeah, I'd do that. Wouldn't you?"
"Oh, for sure, yeah," Tennant answered, adding: "We're available!"
Obviously this is just pure speculation on their parts, but perhaps such a movie is the best way to go at the moment? The series takes a break, does a big theatrical movie with its two biggest stars, and then sets up how the series will continue. That would allow more time to find a proper, permanent showrunner (if there is one to be found) while keeping the franchise alive in a different form.
Of course, the big question is how would one make such a film accessible for non-Whovians, especially if Piper and Tennant presumably return as their recent Doctor incarnation and all of the baggage that comes with them.