Actually, this is the latest I can find. NPH saying that he and Joss are both interested, but that finding the time to do it is key. http://www.winnipegfreepress.com/opinion/blogs/oswald/Some-truly-wonderful-absolutely-Horrible-news-82068467.html
It was published Jan 19, 2010, and he refers to “this” break not being likely, so maybe “next” break. (the break being from April to August. So if that came to be, it would mean it would be produced in summer 2011, which – depending on format – could mean a release in Fall 2011 or any time thereafter. But this is all pure speculation, of course.