Kamyar, I think that future of web-programming is a fast non-devouring functional application.
Users don't care at all is it MVC or not. They don't care what is inside at all.
Is an application a developer toy or an application for people to use?. That is a real question.
The main programmer's principle - don't touch what works fine.
The most conservative part of any application is the data layer. It's the last thing to touch for a professional programmer.
MVC is an option for new applications and a supplimentary option for existing ones.
MVC requires times more time than a WebForms application. In some cases it's useful - i.e. e-commerce and if I need write such an applicaton my choice will be surely MVC..
Let's imagine you have a WebForms application.
Your users need new features, but instead of it you waste your time rewriting it to MVC...
I sure that if you make things like this - your users will finally pay cold feet to it, because competitors make it more and more attractive for users, and you can offer them only new bugs in a previously working functionality .