Question: I'm wondering if there is any news about a "Android Dev Phone 3"? Is an updated hardware of the "Android Dev Phone 2" that is coming soon? (probably an unlocked version of the Nexus One)

Answer: 
The Nexus One IS the unlocked version of the Nexus One! It's sim unlocked and the bootloader is unlocked.
"The Nexus One is no longer available for direct purchase from Google, but will be made available through a partner for sale to registered developers. Please check back for more updates regarding developer availability."
<http://www.google.com/support/android/bin/answer.py?hl=en&answer=166508>