In a Recent Interview on What's on TV magazine, David Tennant expressed his thoughts on Matt Smith playing the Eleventh Doctor and revealed that they had a 'Doctor to Doctor' talk and said that Matt Smith had the 'Right Idea' on Playing the 900 year old Time-Lord.
"We chatted on the phone not long ago and we did exchange a few opinions on what’s about to unfold for him, but advice is a very dangerous thing. Matt’s got an extraordinary journey coming up in all sorts of ways and I’m sure he’ll find his own way through it."
"I could tell Matt was very up for it, though, and excited in all the right ways. He says he’s going to take it very seriously and he seems to have the right idea about playing The Doctor, so far as I can tell."
Matt Smith will take over as the Doctor next year in Series 5. And Tennant will continue to play the Tenth Incarnation for specials due to be broadcast in 2009 and 2010.