The answer in short is that MQ is not about servicing Whidbey. The MQ milestone is about changing processes and making improvements on these processes. It is NOT about code churn, adding features, or fixing known bugs in VS2005.
We are extremely happy with the quality of Visual Studio 2005 and our goal is to keep the quality of VS extremely high during the next product cycle. The MQ milestone will give us the time and resources we need to improve our processes so that enter the Orcas and Whidbey Servicing cycles with high quality code and maintain this quality throughout.
MQ is about internal improvements to our teams, our tools and our processes.