Doctor Who Theory: Why We Won't Meet The 14th Doctor Until The 60th Anniversary
4. Jodie Whittaker's Already Finished Filming
Earlier this month, the BBC posted that Jodie Whittaker had finished filming her tenure as the 13th Doctor, giving the implication her regeneration scene is now done. She's also claimed in recent interviews that she hasn't met the next Doctor during the regeneration scenes. We're still over a year off her final episode being broadcast and over two years until the 60th anniversary. The obvious question here is: would a new Doctor be cast over two years before their full debut episode airs?
It's not impossible given the production values and budget needed for Who, but it is a bit of a stretch. While previous Doctors have arguably had a good 12 months to get acquainted with the role, this is the longest stretch in Nu Who history that a new actor would be waiting to come into the role properly (not counting their initial regeneration scene).
In this writer's opinion, the answer here is simple: the next Doctor hasn't actually been cast yet, because they're not needed yet. The BBC has something else in mind...