Look, we're going to come right out and say it: We have no idea what's going on in Redmond. First, they redesign the entire Dashboard to fix UI problems ... only many of those same UI problems still exist (try finding the latest XBLA release any given week in three actions or less). Next, they announce "Destination Arcade," a "brand new recommendation engine & visual browser app" that promised to deliver a more powerful, dedicated XBLA browsing interface. And now, as communicated by Major Nelson's update, Microsoft only plans to deliver that application for one month.
We've asked the good Major to clarify if the application will simply not be available for download following the 18th or if it will cease functioning as a service entirely after that date. We're not sure we understand either scenario.
Update 1:10pm: Major Nelson told Shacknews, "If you have downloaded it, it will continue to work." But that still hasn't answered the question of why it will only be available for a month.