Alas, the sixth book is out, read, and leaves us dying for more. From things mentioned on J. K. Rowling’s website (I prefer the text-only version), it seems that she will not start working on the seventh book until next year. I guess we’ll all have to just wait, then.
Until then, however, we can stoke ourselves on such tidbits as The Interview. It seems, from the horses mouth, that Ms. Rowling granted an interview immediately post debut of Half Blood Prince. This interview was given by the operators of the-leaky-cauldron.org and mugglenet.com.
The interview contains serious spoilers for Half Blood Prince and indicates story arcs that will NOT take place in book seven, so if you’re interested in being entirely surprised by the last book, I would not read it. It does contain some very tantalizing pieces of information that would be of interest to a Harry Potter fan.