All models of the original Zune, flash and hard drive will be officially discontinued and replaced with the Zune HD.

Paul Thurrott also advices: If you're choosy about colours, don't pre-order, because you'll be stuck with black for the 16GB model or platinum for the 32GB one. But if you wait till September 15th, then you'll get to choose the colour of your choice.

Source: Gizmodo