Moreover, this is not even the first time that a companion has returned to Doctor Who after disappearing for a certain time. Therefore, it is very much possible that Peter Capaldi was simply referring to Clara still existing in his memories. There will not be an actual presence, portrayed by Jenna Coleman.
Doctor Who is yet to begin shooting and if Capaldi did shoot anything with Clara, it was certainly for the spin-off named Class. This spin-off series is set in the school in which she worked during the last couple episodes of the series.
Latest reports indicate that Chiwetel Ejiofor actually turned down Doctor Who. Over the course of fifty years, Doctor Who has been played by 12 different actors and whenever a Doctor decided to step away, another actor stepped in, after he regenerated into a new form.
Fans kept wondering when the show would stop casting white men as Doctor Who and finally introduce a Doctor who was a woman and black. Stephen Moffat, the showrunner, revealed that the role of the 11th Doctor was offered to Ejiofor but he declined.
Stay tuned for more updates on Doctor Who!