Here I found some interesting information. As a Developer (with a MarketPlace Developer account) you will be able to unlock a limited number of devices. Which means that no special devices will be needed for testing your applications.
The rumors we were hearing last week are
true - Developers will be able to unlock devices without having to buy
special "unlockable" devices. Pretty cool - All you need is a phone, a
$99 per year developer account, a mess of free tools, and a dream to
start building!
The full story can be found here.