Today Apple released Safari 6 for OS X Lion users, and download page now makes no mention of Safari for Windows. The Safari download page used to allow users to download either the Mac or Windows version. Now the page highlights the features of Safari 6 on the Mac.
Though there is no reference to Safari for Windows, it hasn’t been removed entirely. It remains at version 5.1.7, buried on Apple’s site. I have several guesses as to why Safari hasn’t been updated for Windows. First, Apple likely put all of their wood behind one arrow and made sure the version for the Mac was ready first. Development of the Windows version may still be underway. Second, Apple may not be able to implement some of the flagship features such as Reading Lists, and the new tab view on the Windows architecture. This is purely a guess as I am not a developer.
Regardless, Safari for Windows still exists. You just have to hunt for it at the moment. My gut says it has been put on the back burner for now, but updates of some fashion will resume.