Last week at the Alt.Net conference, Micosoft pre-announced built-in support for the Model View Controller pattern in ASP.Net. One of the advantages of an MVC pattern is the cleaner separation between the data, process and presentation mechanisms within a given application, allowing for easier adjustments to changes in process.
The MVC support will be released as part of a new ASP.Net MVC framework and more details will be announced in the next few weeks. Because of the nature of an MVC application, the ASP.Net MVC framework will not use the existing post-back model for server interaction. As a result, no viewstate or other similar elements associated with the page lifecycle will be supported. Instead it looks likely that all server interactions will post back to a specific controller class instead. I'm guessing that this uses a variation on the cross-page postback model introduced in ASP.Net 2.0 but without the page state.
There are currently no specifc release dates but it looks likely to release sometime in the first half of 2008.
You can get more details on this from Scott Guthries blog post on this