See the post daid made about pluggable unicorn. We removed the 'generic' GUI stuff from Cura and made a framework (now aptly dubbed pluggable unicorn) which supports plugins for almost everything (file loaders/savers, view rendering, input/output/ switchable engines/backend, etc). This makes the entire thing more like a game engine, with cura being just one of the games built on the pluggable unicorn engine.