The episode where the Doctor reconnects with Sarah Jane was two weeks ago. Last week, he encountered Madame Pompadore. This week is the start of a two-parter, which should be mucho nifty.
I don't play the "I like this Doctor better than that Doctor." I've seen too many regenerations to fall into that trap. Sad, though, that they won't be able to do a "Ten Doctors" special, they way they've had "Three Doctors" celebrating the tenth anniversary of the show, and "Five Doctors" celebrating the twentieth.
Sadly, the first three Doctors are gone now. The Second Doctor, Patrick Troughton, died of a heart attack while at a Sci-Fi convention in Georgia. Third Doctor Jon Pertwee also died of a heart attack. First Doctor William Hartnell passed away not too long after appearing in "The Three Doctors" - it was his poor health that prompted the series' creators to regenerate the character in the first place. Another actor, Richard Hurndall, played the First Doctor for the "Five Doctors" special... and passed away shortly after that!
But that Hurndall was able to take over a part, even for just one story, underlines a major part of casting The Doctor. Each Doctor, from the Second on, has been a highly idiosynchratic fellow, deliberately different from the Doctor that preceeded him. There are no replacements for Troughton, or for Pertwee, and certainly not for Fourth Doctor Tom Baker (who is now far too old to play the role again).
So I doubt that we'll see a reunion of the Doctor's former selves in the new show's run. On the other hand, I would love to see Nicholas Courtney brought back once more (or maybe twice or thee times) as the Brigadier. Sure, he's aged, but he's human! Unlike the Doctor, aging is something we do quite well.