Twitter and tumblr practically went into meltdown this evening after the BBC Entertainment Team tweeted that Matt had said in the NTA press room that he had "no plans to leave Doctor Who" whilst the Radio Times tweeted that he had "one more year of Who" and that "Hollywood beckoned".
DWMTweets however, appear to have clarified things somewhat:
"We're being asked about Matt Smith. He has said he has "no plans to leave Doctor Who." He begins shooting the new series next month."
"Re Matt Smith's direct quote: "I have one more year of Who." That doesn't mean he is leaving afterwards. He says he has "no plans to leave."
"Matt has always said that he takes one year at a time. Anyway! Congrats once again to Matt and Karen, hope they enjoy their night!"
So, there you go. His "one more year" comment is perfectly correct and logical - his contract is for one more year - and that doesn't mean he won't sign another afterwards.
Of course, there are rumours that Season 7 and 8 will be filmed back to back - hence the "long" production this year. If that's correct, then once filming is finished, there will probably be at least a season (if not more) in the can ready to be transmitted at the BBC's leisure. That leaves Matt a fair bit of free time - I'm guessing there will be quite a break before Season 9 starts filming - so it's perfectly understandable for Matt to go off and do other things.