Since ASP is part of the OS, its lifetime is tied to OS support. That means even if ASP is never included in any future OS (extremely unlikely) it is supported as long as Server 2008. Which is at least until 2018 or so.
Though why you'd start a commercial product in ASP nowdays is a more confusing question.
Jeff
Look for Wrox's new book Professional IIS 7 in your local bookstore, or order now at
Amazon.com