The problem is you can pretty much use PHP at will within MODx. That’s what has historically been considered the framework aspect, in that the code you author as snippets and plugins can access the core facilities for working with users, security, and documents. So creating any component in MODx is using it as a framework in a sense.
Revolution will feature more of a RAD framework API that can be used both internally by components, or externally by other PHP scripts, making it more of a true application framework. It will also feature xPDO, which provides a rich layer for working with custom databases/tables; though I use xPDO even with the 0.9.x versions of MODx to create components that access custom tables. You can use just about anything you like to do the same, as long as it doesn’t hijack the MODx database connection, and the same goes for other libraries and PHP code. With a little bit of adaptation, many scripts are easily converted into MODx components.
And if "Revolution API" is not a cool enough name to refer to the MODx 2.0 API, then we have some other code names ready that should fit the bill...