You can use whatever framework you want or implement your own MVC. Parsley offers this out of the box.
Cairngorm isn't supported with Flex 4+ anymore. I recommend using other frameworks for this. For me, I use Robotlegs.
I believe Cairngorm 3 is built on top of Parsley. There's not really such an animal as MVC that would work as the basis of a Framework (and true MVC isn't really possible in Flash anyway http://www.as3dp.com/2010/03/01/separated-presentation-the-classic-model-view-controller-p attern/)