Microsoft officially posted details that confirm the October 11th event and details out the events agenda of the Windows Phone 7 launch. The event will be held from 3-4:30PM at the NYC Microsoft Technology Center, and according to the the announcement also confirms that T-Mobile will be a launch partner. The announcement states "enjoy light snacks, beer and wine while you get hands on for an exclusive showing of T-Mobile powered Windows Phone 7 devices and an early preview of some of our applications that will be available for launch".
In a related news, Paul Spain on Geekzone NZ says that "based on what [he's] been hearing [he] expects handsets to be available to consumers around the world." The dates of availability may be:
Australia/New Zealand - 21 October 2010
Asia - from 21 October 2010 (availability varies by country)
Europe - 21 October 2010
USA - 8 November 2010