Wow, looks like I've missed a couple pages of great discussion!
Here's one I'll throw out there for a good debate:
They should make a special episode and call it
The Four Doctors. Weve had The Three Doctors, The Five Doctors and even The Two Doctors, so why not four?
You could have, of course, David Tennant (the current Doctor), you could bring back Christopher Eccelston (the first Doctor for many new viewers, it would be great to see him again), you could bring back Paul McGann (whom we only got to know very briefly, if at all) and to round it off, Sylvester McCoy (as a bridge/link to the classic series.)
Yeah, itll probably never happen, but never say never! Im sure it has been the fantasy of many Doctor Who fans for decades to see Daleks fight Cybermen, and RTD has given us that treat, so who knows!
Seriously though, as I mentioned with the whole UNIT thing several pages back, this might alienate some of the newer viewers who dont know anything about McCoy and McGann however that being said, they have successfully reintroduced Sarah Jane, K-9, the Autons, Daleks, Cybermen, etc. in the new series so far with great success, so why not!
Just a crazy thought I'd throw out there for discussion.