Las Vegas, April 12th
Microsoft today announced the Internet Explorer 10 Platform Preview for deveopers, which can be downloaded from http://ie.microsoft.com/testdrive/, where code will be refreshed every 12 weeks. The new platform will "push the boundaries of what developers can do on the web even further" and includes "support for additional standards, such as CSS3 Gradients on background images and CSS3 Flexible Box Layout"
Additonal partnerships and demos, including Foursquare were showed off as well as Namco which can be viewed at http://www.microsoft.com/presspass/events/mix. No word on Windows Phone support for IE10, though presumably it may come with "Windows Phone 8" sometime in 2012.
Update: IE Blog has much, much more info on IE10 which can be found here.