I would like to see “plugin” functionality added, to dynamically download and add libraries to the IDE. Something similar to eclipse.
Intellij Idea has a similar functionality. There is a menu with a search option, and you can then read descriptions of libraries, and download them on the fly.
I think you would need to define a way to package these plugins, and prepare a repository.
This could allow the arduino IDE to be fairly stable, but new functionality could still be added without major revisions.