Will Sitepoint be publishing a book on HTML5? If so, when?
Instead of waiting for Sitepoint to get around to publishing an HTML5 book, go now and get the book by Bruce Lawson and Remy Sharp.
At a guess I would expect that they probably will.
I also expect that they will publish one long before HTML 5 becomes a standard and half the book content will be wrong by the time it does become a standard.