In truth, what little I know about HBO's intentions regarding a "John from Cincinnati" DVD set boils down to this: Yes, they intend to put one out, but it won't be until next year. People who know more about these things than I do say that it takes a long time to master and "author" 10 hours of material for DVD, not to mention assembling packaging materials and marketing plans, etc.
Plus, how could you put out a DVD set of David Milch's spiritual surfin' safari without packing it with all kinds of cosmic extras, from commentary tracks (even if it might sound like a post-grad English lit course) to deleted scenes and behind-the-scenes hijinx. (Can you imagine the outtakes? Tee hee.) Certainly, all of the original viral-vid material produced during the run of the series would be a natural to fill out a nice bonus disc. They could even incorporate some of the puzzles and such that are built into the faux fan websites that have distributed this material to date, as chronicled here two weeks ago in this post.