Windows Phone 7.5, better known as Mango, could possibly-maybe-there's-a-chance be out September 15th, according to the latest round of rumors.

Previous rumors had already pointed to the 15th as a possible release date, and now those have been backed up by the same sources that accurately predicted the release dates for the Mango dev betas. For what it's worth, though, previouser rumors had the release date set for September 1st, so take this with some quantity of salt.

We're rather a lot excited about Mango, which brings the Windows Phone platform some much-needed necessities, like visual voicemail, and also some next-generation luxuries, like baked-in Twitter support and a Hulked-up Bing.

The release shouldn't be quite as fragmented as an Android software upgrade, but we also wouldn't be surprised if it's not immediately available for every WP7 handset, either. [Liveside via Winrumors]