MarkB
Legend
Wonder if Moffat's intention is to do a complete reboot, and start anew with Capaldi as a new 1st doctor. (ie. Throw out all the existing canon and continuity of the past 50 years).
Perhaps similar to JJ Abrams rebooting Star Trek in the 2009 movie.
Since Capaldi's already appeared (well, bits of him) alongside all the other incarnations, that seems unlikely.