Today, the slew of "pre-Mango" posts began. Were you suspicious about why the sudden posting? It's because Microsoft has been giving out the build to the press ahead of the Mango Beta release, which is due to be announced within the next 24 hours.
Neowin has received multiple independent tips that the beta will be made available for all devices through the MSDN Create hub for those with developer accounts, on June 22/23, with Microsoft set to make the announcement sometime during the next 24 hours. The beta will not be restricted to "favorite" developers but will be generally available to anyone with a paid subscription, and will be able to be loaded on any of the production devices.
The timing of the claims line up, as do the legitimacy of the claims considering the amount of reviews that have just appeared. Also, if you look at multiple reviews, each one uses a different device. There aren't any Mango events worldwide for this specific launch, so we expect a release will appear on Microsoft's PressPass site soon.
Mango brings a new set of features to the platform, including IE9 support, full IM integration, performance improvements and multitasking and is expected to be released in September of this year for general availability.
Update: Neowin used multiple sources to comfirm this news. The sources used to confirm this article are reliable, and this news is not considered a rumor currently. In addition, the software giant is planning on handing out developer devices to VIP devlopers as part of the announcement.
Update #2: If you weren't convinced yet, Microsoft Addict says that "After asking around, [they are] hearing murmurs of a June 22nd release as well."
Update #3: It seems that not all is clear on the release of the beta, Brandon Watson states on his Twitter account that "Press reviews of consumer features are only thing happening this week." At minimum, you will begin to see full reviews of 'Mango', but speculation on if a beta will ship this week continues.