UPDATE 02JUN16 0001z:
Just like that, already out. You can buy it from the product page.
Umberto, over on the FSDT forums may have accidentally revealed that their upcoming Memphis scenery will be out before the weekend is up!
Here’s the quote from the forums:
You can disregard the update notification message, because it only happened because we are updating the download servers for the new KMEM release and GSX release, which will happen very soon, most likely before the weekend.
We’ll keep you guys posted if this is the case.