Files without a dedicated application will be the exception rather than the rule. Movies, Photos, Documents, spreadsheets, databases, music, books; you will usually open in a dedicated application. It's not hard to envisage an improved UI for files that do not have a dedicated application: they could be presented in a view showing all the files that are not associated with a program, for manual association. From then on, the system would know which file types to present along with that application. In addition, it goes without saying that full access to the underlying file system should be possible for developers and those that need it (which will be a tiny fraction of the userbase).