Microsoft's latest update to its Windows Phone OS, codenamed Mango, may arrive sooner than many were expecting. Fujitsu will offer the very first Mango device, a waterproof phone called the IS12T, on KDDI as early as late next month, according to the Japanese publication Nikkei.

The phone will go for somewhere between 30,000 and 40,000 yen ($380 and $500), which is not that much given it will probably be a higher-end device. Of course, we won't know if that's really a good deal until we see all the Mango phones from Microsoft's various partners, a list which keeps growing.

Last week, Microsoft showed off four unannounced Windows phones from Acer, ZTE, Fujitsu, and Samsung. Nokia, which agreed to switch to Windows Phone as its primary platform, will also offer multiple Windows phones; the first one is codenamed Sea Ray.

Windows Phone 7.5 (codenamed Mango) is expected to begin rolling out this fall (check out our preview from last month). 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.