Hi there, me here. Hopefully I didn't miss any news about the Collectible Minifigure Series 4 launching somewhere while I was out, but the April LEGO Store calendar further reinforces my belief that they will debut somewhere this month.
Toys N Bricks shares the April calendar which lists April 15th as the date Series 4 will be in the brand stores. Historically, the brand stores have been late to the game with other retailers like ToysRUs beating them to the punch (at least in the US any way). Who's also to say that the US will get them first again?
The Series 3 Rollout Map via Google turned out to be helpful, perhaps it's time to put up the Series 4 Map, eh?
You can see the full calendar at Toys N Bricks. Did I see that correctly? Series 1 minifigure elements will be available via the 'Build A Mini' kiosk in stores?! Nice...