I’ve already had a couple of questions about how to develop applications for Windows Phone 7. At the moment the “developer story” has not been announced but over on the Windows Mobile Developer Blog they have announced that MIX10 will be where they discuss how to develop for Windows Phone 7:-
Attendees will have access to a dedicated Windows Phone track (currently the 12 sessions are unnamed) and access to the Windows Phone 7 developer tools:-
http://live.visitmix.com/News/Exclusive-Windows-Phone-7-Series-Offer-for-MIX10-Attendees-WP7