Microsoft is planning to make available Windows Phone "Mango" developer handsets as early as next week. It is said that these handsets will be given out in several rounds, however, the exact device model is not yet known.
However, not all developers will be given one.
According to a tweet from Microsoft's Director of Developer Experience on the Windows Phone team, Brandon Watson, the devices will only be made available to "serious developers", and must make a connection with their local "Windows Phone 7 Mobile Champions":
We will have devices for serious developers who take the time to reach out to MSFT and get to know their local mobile champ.
Microsoft had been using their ASUS E600 devices for various Windows Phone "Mango" demoes, and this is the unit which were given out to limited third-party developers before Windows Phone 7 was released last year.
Microsoft had also been using HTC Mazza, which visually looks similar to the HTC Trophy but with updated CPU and GPU and features a 12-megapixel camera, for their recent demos during the Windows Phone "Mango" VIP Press Event.