Hardly premature with a 2009 release and its already august. Besides Jordan has completed most of it if not all of it already (at east in rough form) according to previous interviews and I'm sure there is some sort of plan to release it onto the market in new printings of KOD as a preview after the epilogue (As was done with other paperback books in the series!). And all of that takes time to enter the market...any prologues wont just be an online release.
Brandon may not have finished it up yet, but he will have to soon!
Those of us who have waited for every new release since the 90's are just a little too eager to see a piece! lol
Let me paraphrase what Tor has always said about the WoT books. They'll be released as soon as possible after they're ready. That being said, I don't believe that Brandon really has much say in whether the prologue gets released early or not. He's writing this book under contract with Tor and Harriet, so he has less say in the release process than he normally would with one of his other books. Obviously he can delay it being released by not finishing it, but I don't think he'd do something like that to us. As for your assertion that since its august already and the book is slated for 2009 that its not premature. Let me remind you that 2009 != January 1, 2009. Its scheduled for a Fall release, still more than a year off. The only deadline before January 1, 2009 is the first draft due at the end of December. If the prologue got released early, I wouldn't expect to see it before September 2009.
Sure it'd be nice to see something now, but after 16+ years of waiting to see how it would all finish I won't be too terribly upset if I didn't get the prologue a month or two early.