I've given this the weekend and Monday to see if Frogboy mentioned this in one of his updates. If he has, then I've clearly missed it and apologise pre-emptively.
My local retailers that are a bit more on-the-ball than the others posted the new release date on their websites on Friday evening/Saturday morning (+2GMT) already. The rest caught up yesterday. Checking out Amazon in Germany and the UK also revealed the new release date while France claims to have received the game on 7 May already and are currently out of stock. Most Australian online retailers I checked out claim to have the game available for purchase already while others have it for pre-order without any release date.
So what's going on? The international retail release was pushed back a week without any official news (that I can find) from Atari or Stardock. Did Stardock request it be moved in light of the final multiplayer fix only being scheduled for release late this week?