the last series of Doctor Who was similar, in that things that happened at the beginning of the series happened at the end, and even the first episode, with the Doctor bumping into Martha and giving him his tie at the start of the episode, and us not knowing why until the end.
My idea is that RTD is trying to wrap up the first 4 series and bring them round full circle. RTD has a habit of including little throw-away lines like this - yes it was obviously a joke - but that isn't to say that it isn't significant. I'm not saying that Richard Wilson's going to come back or anything, but, it fits nicely into the theory that the series is going to end up full circle.
So....you've got references to Doctor no 9, Rose re-appearing and rumours of more scenes shot at the location they filmed at the end of series 2 (not to give too much away).
My bet is that the story will be effectively wrapped up for the Christmas special, meaning that they can do some new stuff for the specials next year, in the absence of a proper series. Given the length of time between the specials next year (I would imagine) that there will be little room for a continuous story, casual viewers just won't be able to keep track if there are only 3 or 4 specials over a year.