That's highly doubtful based on precedent.
If RTD had been locked in to return for months, his return would've been announced when Chibnall and Jodie announced their departures based on past precedent.
P
In addition,, past precedent from both the Classic and Modern eras of the show indicates that the search for a new Doctor begins only after its announced that the current Doctor is leaving, which barely happened a month ago.
Maybe they've been 'avin' a larf watching us speculate and argue about the new showrunner.