Google Nexus one is unavailable to sell in its official website permanently as said by Google that it has achieved the initial aim.However,it will be sold at some authorized retail shops as well as partners in US,European countries and South Korea.On the other hand,it will be also treated as a developer phone and sold by Android develop team in some other ways.I just caught the announcement from Android developers blog about it:

Nexus One Developer Phone

from Android Developers Blog by Tim Bray

We’ve always offered unlocked phones for direct sale to registered Android Developers. As of today, the Developer Phone is the Nexus One, at a price of $529. To see the details or order a phone, you need to sign in to your Android developer account and click on the "Development Phones" link.

The Nexus One combines an up-to-the-minute platform (Android 2.2), modern hardware, and the pure Google Experience software suite. It’s a good choice both for people who want to build Android applications using either the SDK or the NDK, and those who want to experiment with modified versions of the Android platform. Note that the Nexus One still ships with Android 2.1 but will download 2.2 soon after you turn it on; make sure you’re near a fast network.

As well as being an outstanding developer platform, it’s a really nice everyday phone; we’re really happy to have connected the right dots to make this happen.

So if you are an Android developer,you still can use that provided method to get a new Google Nexus One which has advanced hardware and designs.If you’re not,you can find some way to get it too.Google Nexus One will never die.