That's what the Guardian said in a tweet moments ago!
But the URL is dead.
However, calling up search reveals this:
Update: Moments after posting this, I clicked on that search link and found the Guardian has apparently deleted the item! WTF? I'm glad I got the screensnap!
Update 2: To be sure I wasn't losing my frikkin mind and that I'm not playing some sort of hoax here, I retrieved the tweet from Twitter itself:
Click = big
Update 3: BBC confirms Tennant is leaving Doctor Who:
Thanks to a Guardian screw-up, I had a world exclusive there for a few moments.