This just made my day, Mugglenet is reporting that JK Rowling is working on the Harry Potter Encyclopdia!  They state:

Ian Rankin, a friend of J.K. Rowling, revealed that the last time he saw her, she was working hard on the Encyclopedia. He also mentioned he saw her drawing up family trees.

It should be mentioned that Rankin said he has not seen Rowling in some time and that he didn’t know whether the encyclopedia was for her own fun or not.

I would like to add that even if she is working on it now, it still may be YEARS before it comes out, she had said after Deathly Hallows came out she would be taking her time and not rushing anything.  But its good to know that she has at least been seen working on it.