Classic ASP is actually a part of IIS product wise. That said, Microsoft will support ASP as long as it is a part of IIS. Since it is part of IIS 7, and Microsoft's default support length is 10 years, it is likely to be around until at least Feb 2016 since IIS 7 was technically launched in 2006 with Vista, though, it will probably last until 2018 due to Server 2008 being released in 2008.
Now, I am not a Microsoft Employee, so I can't speak for them, but this is what I believe.
If you need a gaurenteed answer, I would call Microsoft product support. However, I don't think it is going anywhere anytime soon.