We know from the first book that Dumbledore guessed what Harry must be seeing in the Mirror of Erised (his family, assuming Dumbledore cannot directly see the Mirror anyway - which could be a possibility since he could alter it).

In the chapter in which this happens, JKR doesn't immediately reveal what Dumbledore sees when he looks in the Mirror.

Is it later revealed by JKR what Dumbledore sees when he looks in the Mirror of Erised?