I (and others) stand corrected. The Doctor Who News Page item has been updated to indicate there will not be a Christmas Special edition after all. As originally posted above, the final episode will indeed air this Saturday.

I really feel sorry for the Confidential crew because presumably they are in the midst of producing the Christmas edition.
I don't think Dr Who needs spin off shows to be succesful.
Oh I agree with you there. The point I was making is that for whatever reason (and several blogs in particular Kasterborous have been writing a lot about this recently) a fair amount of UK media have started to act like sharks in the water with regards to Doctor Who, claiming (often via creative interpretation of things like overnight ratings numbers) that the series is fading fast. This despite other evidence to the contrary. The cancellation of Doctor Who Confidential in my opinion will just add fuel to that fire, even though the series never needed Confidential to be a success. Nor did it need SJA or Torchwood, for that matter. It did perfectly fine on its own for 26 years, after all.
But there is still something to be said for a series "spearheading a thriving franchise" and we can't really say that anymore. Torchwood is in limbo and may or may not return (that's up to RTD and Starz), SJA of course has ended through no fault of anyone's (no one blames the BBC for that decision; much as we like the supporting characters a Clyde and Rani series really wouldn't have been viable - Sarah Jane was the show), and K9 may or may not be back for a second season and the impression I get is we're lucky if 1 in 50 Doctor Who fans have ever even seen that one. And the other behind-the-scenes shows - Torchwood Declassified and Totally Doctor Who - are long gone. It's just a shame.
That said - the fact the franchise has contracted to one core show isn't necessarily a bad thing because it might open the door for, indeed, another spinoff, whether that be Vastra or something else. Plus I can't imagine the BBC won't commission some sort of documentary series for the 50th anniversary.
Alex