This is great! This tells me that Windows Update now has a streamlined path for new features and updates to current Windows-bundled applications. In the past, Microsoft has been very timid about updating programs bundled with Windows, which is one reason why Microsoft pulled many of them out into Windows Live. (Internet Explorer 7 was a big deal to update. At some point Windows Update in XP would open up the installer, right in the user’s face. The alternative would be to update IE automatically, that’s not fair to the user.) Microsoft would never push a new program (with a whole new UI, etc.) to an end user without asking first, and it seems that this path allows Microsoft to easily ask that question. (The question would be queued in the Action Center maybe?)
Since I’ve had the Windows 7 Beta running for a few weeks, I’m guessing that this Windows Update type was itself an update, which just goes to show the extreme flexibility of Windows Update.
I’m looking forward to the release candidate in April!