It has reportedly now been confirmed that the next Ghibli film is Miyazaki's adaption of the Chinese children's novella I Lost my Little Boy, the cover of which you can see above. As far as I can tell, not being able to read the book, the story revolves around a young chap dying from heart disease - but isn't at all downbeat... well, not for most of the page count, anyway.
The oddest thing about the project is that the book is very obviously inspired by Miyazaki's previous films, and, I'm told, even makes mention of Totoro as though he actually exists right at the very top of the first page.
So, to recap: a Chinese author wrote a children's story about dying from heart disease, set it in the same universe as a number of popular Japanese anime (many of which didn't share a universe in the first place) and now, the studio and director responsible for those anime and adapting the book into their next film.
That's the sort of stuff that makes Quentin Tarantino fall over all giddy with excitement.
[EDIT: While you're here, checking this very-heavily-linked-to-story out, please take a scroll down the main page or throw a few terms into the search box. There are several good stories that haven't been picked up on much yet - including the first still from the next Coen Brothers film, an extensive set of Spider-Man 3 spoilers, details of Subtle Knife scenes already being shot and much, much, much more]