Amazon has modified the Versus XIII page again. Now says "Sign up to be notified when this item becomes available". It is not directing to other sellers now.
It appears that Amazon is no longer selling Final Fantasy Versus XIII directly, and is now only pointing to other sellers. Amazon was selling it a few days ago.
Here is the current page, and here is one from 9th Oct, 2012. The Japanese page is also the same, i.e., pointing to other sellers. Also notable is that Lightning Returns is still available for preorder.
Could it be that they are preparing for some changes at E3?