It seems the “episode without the Doctor” possibility is really driving fans nuts. We've already had Love and Monsters in series two, and the expectation is that there'll be another episode that's Doctor-lite, thanks to hellish filming schedules. So how will the production team cope?
We've already had one possibility thrown at us: the Doctor and new companion are regressed into children by mad scientist Mark Gatiss and so child actors will take the place of Freema Agyeman and David Tennant. Since there's that exciting competition for some lucky fan to land a part on the show, maybe that'll tie in nicely.
But now, we have another one, which has the virtues of a 1% chance of being true and all the hallmarks of a conspiracy theory. In this exciting possibility, Martha Jones turns round, says “Tell me all about regeneration, Doctor”, and low and behold, we have a Tennant-narrated tale of life being Paul McGann. That would fill me with joy if it happened, because it's about time McGann got to be something more than a footnote in Who history*.
Where the conspiracy theory element comes in is the BBC7 series starting in the New Year. The idea is that that will act as a primer for the public to accept McGann as a previous Doctor and more importantly to get them used to Sheridan Smith as his companion, who will then legitimately be able to appear on-screen as the Doctor's companion and be an audience draw. Smith, of course, has a big youth following from Two Pints of Lager (although not from Grown Ups).
Not at all plausible, particularly since the rumour also says it's going to be set during the Time War, but I liked it anyway.
Incidentally, the Big Finish web site now has more details on those BBC7 audio plays. One thing I spotted that I hadn't seen elsewhere: Sheridan Smith's character is going to be with the Doctor thanks to some form of Time Lord Witness Protection Programme (very Big Finish). Even she doesn't know what she's supposed to have seen, though.
*Footnote: Technically, Paul McGann is the longest running Doctor, since he was the official Doctor between 1996 and 2005, appearing in the TV movie, comics, books and audio plays, all of which were licensed by the BBC.
UPDATE: The rumour mutates and combines with the earlier rumour! Now the suggestion is that when the Doctor and companion are zapped by Mark Gatiss, he turns back into Paul McGann. Now that's the hallmark of a great rumour.