Apple going to Postfix and Cyrus IMAP

Well, I think it was rather predictable that Apple would make further dramatic changes to their server software. http://www.macnn.com/news/19862 I just finished successfully configuring my new mail server, but its using Exim and Courier not Postfix and Cyrus. Not sure if I should stay on the server I have been using for years and hold off the migration or what. I hate to move all the user accounts only to have to move them once again in six months. If I start over and install Postfix and Cyrus IMAP, how will that be effected when I upgrade the server to 10.3?