No need to ask him yet. Right now it's a combination of Matt off doing his Hollywood thing, giving his Doctor more time to recede into the past, and BF having (with Ten and Warrior now added) nine Doctors to make 'episodes' for already, plus the various spinoffs. An Eleven/Amy (or Eleven/Amy/Rory, or Eleven/River) series is guaranteed money in the bank, and demand for it will only grow with time. And there's always the off chance Christopher Eccleston could be talked into the recording booth like Tom Baker was. What's the rush?