Canonrumors confirmed that the new announced EF 200-400mm f/4L IS USM Extender 1.4x will start shipping in late May with limited quantity available.
Canon Canada tells retailers that they will have several in stock on May 27, 2013 in their warehouse. Retailers will have theirs a few days later.
If you have already pre-ordered this lens when announced, it looks like you should expect yours quite soon.
|B&H Photo Video||Pre-Order|