I think the statement that XNA is dead will come as a surprise to the folks in WinPho and Xbox. At the moment, I'm just assuming that the person writing the email was an idiot and was closing the XNA/DirectX forum and noting that XNA Game Studio and Managed DirectX are dead, rather than providing an official "XNA and DirectX are dead" change of strategy type of statement.
For example, calling a technology "legacy" doesn't mean that it's obsolete or abandoned. The day after Vista shipped, for example, everybody in the Windows team called it (Vista) legacy, as opposed to the new OS that was in development, to avoid internal confusion.
That makes perfect sense within the organization, but when exposed to the outside world, where these words have different attached connotations, it creates confusion.
++. Inside of Microsoft, Windows8 and Office 2013 are now described as "legacy" components / applications.
Also there's a strange notion in the press that stuff executives say or any inferred statement from a single Microsoft email constitutes an official position by Microsoft. All too often we see executives saying something silly because they don't know or got the wrong end of the stick, or an email pronouncing the death of a core Windows technology gets taken at face value.
A lot of this is a consequence of Microsoft's abandonment of the press; there's certainly a feeling at MS that "haters gonna hate" and that there's no point talking with the press or doing effective communication because it'll end up backfiring, and so people that should be taught to deal with the press aren't, and the press jump or infer too much from misleading scraps of emails because of an information vacuum caused by Microsoft's inability to have a unified press strategy.
They just need to come out and say what they say all the time internally: That technologies and frameworks have a ten year shelf life, and that Microsoft goes to major efforts to avoid people's apps built on Microsoft's frameworks from ever dying. If developers got that through their heads, they'd realize that Silverlight probably still has a longer shelf life than Flash, that apps written in XNA are most likely going to run on the XBox after the XBox 720, and that Age of Empires will not only run in desktop mode on Windows8, but it'll probably run in desktop mode on Windows9, 10 and 11.
Or to put it another way, for the 99.99% of new apps written for a legacy Microsoft component, the legacy component will still be there, supported, upgraded and actively fixed for years after your app has died for other reasons. Case in point: You can still run edit.com - a program first debutted by MS in 1991 on Windows 8-x86. A full 22 years later.