You'll probably have better luck with your Waterworld question in the Movies area. Costner replacing Reynolds is the rumor I've read before, that's about all I know from the details of that production.
As for discussion it's certainly welcome, the lack of it here is probably due to the lack of...
DIRECTOR FILMOGRAPHY - The Films of KEVIN COSTNER Rank ‘em, rate ‘em, review ‘em or whatever. KEVIN COSTNER Open Range (2003) The Postman (1997) Waterworld (1995) (uncredited) Dances with Wolves (1990)