I asked a similar question a couple weeks ago here and got a reply from a monorail CM whose username escapes me somehow... Basically the news is there's no news. They'll come when they come. Late 2007 at the earliest from a monorail pilot I asked at Disneyland a month ago. 2008 from another. They'll be replaced as they become available. Still, it'll be kinda sad to see Monorail Purple go. I've always liked that one.
On a related note, I saw the inspection car go by on the monorail tracks at about 1 AM the other night. Was pretty cool.
The Right Honorable Count Boogie Bonz of Random, at your service.