Matt Smith has commented to
Io9 on the thought of a multi Doctor story...
"There hasn't been any official talk about it yet. That's still over a year away. But I'd love for it to happen. How amazing would it be to see Tom Baker?! Can you imagine just seeing him back in the scarf, man? That would be amazing! So cool! And Paul McGann is a great actor, man, and a great Doctor. I say bring back Chris and Dave, too! How many Doctors can we get into one story?! Imagine if there were five or six of us in one ep and we could all just look at each other and judge each other."