Microsoft is rumored to reveal a Microsoft branded Windows 8 RT tablet on Monday. I do not think so.
What is official is that Microsoft will host an event in Los Angeles at 3:30pm PDT to make a "major" announcement. The Wrap reports that an individual with knowledge of Microsoft (who is that? Steve Ballmer?) said that Microsoft would, quote: "introduce a Microsoft-manufactured tablet at the event, marking a foray into a new hardware category that would put the company in direct competition with giant rival Apple."
This would be a huge surprise. It would also f@#$ all Microsoft's hardware partners and that is likely again the reason why this will not happen. Unless Microsoft decides to be only company making Windows 8 RT tablets. Theoretically it makes sense for Microsoft to mirror Apple in the tablet market to try take away aggressively market share from the iPad, but Microsoft's current business model does not work here. They cannot alienate their hardware partners with offering a Microsoft branded tablet.