Electronics such as MP3 players don't usually use numbers in the product name when new models come out.. Look at the iPod. It's still called the iPod (for the most part) even though it's gone through many changes. Sure there is the Nano, and the Video, etc, but the iPod Video is actually just an upgraded "Standard" iPod over the years.
I don't see much use in the domain zune2.com unless Microsoft actually makes one called the Zune 2.. and in that case there's still not much use because that domain has "bad faith" written all over it. Sorry.