Microsoft and Nokia appear to be preparing a little announcement for August 17, 2011. Both companies sent out an invitation for a joint-event at this month's GamesCom in Cologne, Germany, according to the unwired.

The invitation tells attendees "exciting actions and surprises will make it an evening to remember." The duo will also raffle three Nokia Windows phones (as soon as available). This would imply that the date is just an announcement of new phones rather than their release.

Nokia's first Windows phone, codenamed Sea Ray, looks nearly identical to the recently-announced Meego-based N9 smartphone, but it's running Microsoft's Windows Phone operating system. Nokia's first Windows Phone 7 handset(s) will be launching in Europe later this year: France, Germany, UK, Spain, Italy, and the Netherlands have been confirmed.

Windows Phone 7.5 (codenamed Mango) hit RTM just last week. The update adds a number of much-awaited features, including an HTML5 version of Internet Explorer 9 for mobiles, deep Twitter integration, better multitasking support, an improved messaging system, new Bing features, and so on.

There is talk that Microsoft is already working on the next Windows Phone updates, codenamed Tango and Apollo. Last year, we heard of that the second major update to Windows Phone will be Apollo, due toward the end of 2012. At some point Microsoft will have to release Windows Phone 8. One of these updates could indeed be Windows Phone 8, or an update to Windows Phone 8.

It's generally accepted that Windows Phone is not selling well. AT&T Mobility CEO believes things will start to pick up with codename Mango and as the Windows Phone Marketplace gains more apps. Nokia CEO Stephen Elop meanwhile argues that Windows Phone scores better than Android and iPhone with consumers, but OEMs are doing their best work for Android. He believes that once Nokia starts doing its best work for Windows Phone, the platform will take off. Microsoft says it dreams of selling 100 million Windows phones per year.