Web dev frameworks vs RIA

How do traditional web development frameworks cope with RIAs?

By RIAs, I am referring to the Flex/Silverlight model (Ajax has
a hybrid model in my view, so I’m not discussing that here since
I don’t want to muddle up the question).

Coming back to topic, I see that the traditional web development
frameworks are inside-out and RIA development as outside-in:

Traditional web dev frameworks RIA frameworks
Flow: controller ⇒ model ⇒ view (pages) view ⇒ controller ⇒ model

Everything built into the framework. View is generated via

View is designed separately and it’s what runs first. Backend
is a bunch of web services.

Question: How is this resolved practically?

For example, how do people using Django or Ruby on Rails actually
write, say, Flex frontends for their websites?

Do they ditch their templates/rhtml? Do they design the RIA first and
then the web service, or the other way around? … etc.

I couldn’t figure out the answer and since there are people out there
doing it, I’m hoping the
i.e. lazy web gods will answer.