Matt Smith makes one ambiguous statement at a convention and next minute everyone from the Mirror to Den of Geek is announcing his return. The Radio Times has it as "Doctor Who: Matt Smith will be back". The quote goes like this: "I’m just waiting for the next anniversary...I spoke to Steven the other day and said ‘what’s the quickest one we can do?’ I love the idea of other Doctors coming back. Also that gives me the opportunity to come back, which I totally will by the way!”
That does not mean he is booked to come back, that simply says that Matt Smith would be happy to take the part if it was offered. Whether Steven Moffat's writing such an episode (it would be Moffat writing it if there was going to be another one) is an entirely different question.
Of course, Moffat being Moffat, there may be an understanding about another special that's been planned in advance, but really, nothing seems to be set in stone here. Don't read too much into it yet.
Oh, and also there's this teaser clip going around of Smith in Ryan Gosling's new film "Lost River". If you have an overwhelming desire to see Matt Smith with no shirt on, today's your lucky day.