I would love to see the extended version on Blu-ray. I bought this on HD-DVD and the picture quality was better than my DVD but I've never seen the extended version which I would buy on Blu-ray in a heartbeat. I've always thought that Waterworld was a good movie and I've never understood the negative reactions to it.
I saw this at my local Best Buy for around $12 today. I was going to buy it but then I thought the same exact thing as what was mentioned here. Where was the extended cut!? Would they really release an extended 15th Anniversary Edition less than a year after the initial barebones release? Maybe. Maybe not. Either way, I guess I'll be holding off just in case...
EDIT: I was just reading the reviews for the extended edition that was released on DVD - it was the ABC version which means while it is extended, the violence is cut down and the cursing is gone! WTF!? They couldn't even release a proper Extended Edition. Now, I have no faith in them doing an all new transfer to Blu-ray with the extended scenes seamlessly cut into the theatrical version (which would allow the violence/cursing to be kept).
While there is undoubtedly more footage available, there is no longer "Extended Cut" sitting around. The only "Extended Cut" that ever officially existed IS the ABC TV version. That's also why the "Extended Cut" is not presented in HD; it was probably edited on tape rather than film, and thus, can only be presented in television-friendly SD with all the language bleeps and whatnot.
Universal is never going to spend hundreds of thousands of dollars or even millions to have a true "Director's Cut" or "Extended Cut" prepared. They would have to remaster all the film (up to four hours' worth -- twice the length of a normal film), pay the director (who notoriously quit the project after a few edits were turned in, leaving Costner to finish the film) and an editor to cut it, have the sound re-edited and mastered, etc. Just not going to happen.
What Universal should've done is just stuck Disc 2 of the DVD inside the Blu-Ray case so that people who bought the Blu could also have the EC. As others have noted, a fan also created a version (just an edit using existing DVDs) with all of the existing footage from the TV and theatrical version.
Eh, I've seen things like that happen before. A few years back, 'Con Air,' 'Enemy of the State,' and 'Crimson Tide' got re-masters and extended cuts for the DVD out of nowhere. It really wouldn't be that hard to do. I guess I'll have to try to obtain that fan edit in the meantime.