Preview at WWDC likely in June, followed by September launch.
Retail Apple Watches Still Have a Hidden Diagnostic Port [Updated]
One MacRumors reader, Louis, was able to slip off the bottom band during his Apple Watch try-on appointment to discover that the hidden diagnostic port on early models still remains in the retail versions.
The presence of the diagnostic port was first reported in March by TechCrunch with speculation that it could eventually open up the market for "smart" band accessories that can interface with the Apple Watch, itself. Apple, however, has made no such promises and doesn't even acknowledge the presence of the port in any official documentation. Louis also reports the retail staff had no training on the use of the port.
Update: John Gruber notes that his review unit has the port, but it is covered up: