I'm in the "Torchwood isn't very good but has some good episodes" camp. I liked Out of Time and Captain Jack Harkness. But it's not important to Doctor Who's continuity in any way that isn't explained in the first five minutes of Jack's appearance at the end of season 3.
MEANWHILE (minor spoilers of upcoming special follow):
Of all the various rumored guest stars, it would appear that
Jessica Hynes is confirmed photographically. She's playing a character named Verity Newman this time, who's published a book called A Journal of Impossible Things with a picture of a fobwatch on the cover -- so presumably she's playing a descendant of her previous character.
This, I'm all right with -- it's perfectly fair for a regeneration ep to serve as a look back at the current Doctor's run (Tom Baker had a sequence where his life flashed before his eyes, with a few key villains and companions in there), and really, for my money, Human Nature/The Family of Blood is the quintessential Tenth Doctor story. Despite the fact that it was originally written as a Seventh Doctor story. And despite (or, actually, largely BECAUSE of) the fact that he spends most of it as a character who is very very different from the Doctor.
I'm not alone in that opinion -- as mentioned earlier in the thread, Tony Lee picked the fobwatch as #10's artifact in the museum in The Forgotten comic series. Granted, it's not as iconic as #2's recorder or #4's jelly babies, but it WAS central to a couple of very good stories (I am counting the first episode of the Master arc as very good).
That and the fact that the journal itself is a retrospective of the Doctor's entire fantastic series of lives.
That could be an entire separate discussion -- Human Nature/Family of Blood as the quintessential Tenth Doctor story, y/n? Girl in the Fireplace would be my second choice. And The Runaway Bride has one of the most important Tenth Doctor moments; pity the rest of the episode is fucking awful.
Anyway. You know, bringing back Rose or Donna could actually work if only RTD could exercise some restraint, which of course he can't. Maybe just a quick shot of Donna waking up in bed, or Rose getting a sudden shiver and Clone Doctor saying "I'm sorry. I'm so sorry." In other words, if they're used briefly and not in a way that undoes the whole super-final, he-can-never-see-them-again, no, seriously ending that he spent twenty fucking minutes on in the finale.
Martha, Jack, and Sarah Jane could actually have story roles, but I kind of hope they don't. (Maybe Martha.) And I'm hoping the rumors of the Master are false too.