The concepts? Sure. It already has been, to some extent at least.
For instance, the JavaFX UI toolkit is heavily multi-threaded and uses a dialect of CSS 2, it has support for blurs, box shadows etc. The app thread renders the scene graph to some sort of intermediate form (never looked at what, but I think it's similar to the WebRender form, i.e. a series of styled absolutely positioned boxes and text regions), then a render thread translates that into Direct3D or OpenGL calls. The render thread may itself use subthreads that handle rasterisation.
