Ok, time to brain storming. My suggestion of disruptive OS (or software) is kind of an AI (Artificial Intelligence) OS :
- software a lot more intelligent than today's standards. Software that could help the user, that learn about user, that care about the user. Software (OS and apps) that is a lot more than current personnal assistants (Google Now, Siri, Cortana, etc);
- software would require AI (Artificial Intelligence), GA (Genetic Algorithms), ANN (Artificial Neural Networks), deep learning, etc. It would run on local device, not on cloud, but backup of data mining of user could be backuped in the cloud, so the power hardware of today's standards would be well used;
- for example, instead of web browser typical use where the user chooses a web site, the "web reader" would show a compilation of articles (from many sources) about the user search. E.g., user likes to read about Linux, last time it has read was a week before, then the "web reader" would show a compilation of Linux news and articles from the last week, following the user preferences, time available by the user, etc. These user preferences will be obtained from (a form, etc, in) the beginning, then from next searches when the user ranks the news (as useful, too short, too long, trustful, etc). The "web reader" could suggest content in some days and hours, learning the user's patterns of web reading;
- a presentation software woud be intelligent and suggest many diffferent layouts (following your preferences and your past use), and even help the user writting the content;
- the OS would suggest installing apps (or modules) tailored to the user's preferences. No need for the user searching which app to be installed from thousands. So, if the user is a gamer (of certain type), do mathematical calculations in college, then a selection of games and math tools would be suggested;
- the "calendar" would be very intellingent after the user filled his/her data (age, etc), schedule, etc. It would suggest actions to the user. E.g., "After one year, it's time to go to the dentist, ok ?". "Tomorrow is time to vote for the political elections, and you need travel to vote in your district";
- even with the OS (and authorized softwares) knowing a lot from the user, there would be privacy by means of local storage, encryption of clouded backup, etc. When the user is on another device, his/her profile would be synchronized from the cloud so all the user knowledge would be shared.

So, in this future OS and softwares, the data (preferences for many subjects, let's say the full user profile) from the user is a key point. The OS would be responsible to manage the user full profile, to keep it secure (in the cloud with encryption, shared between the user devices, etc), to share part of the data with some softwares (authorized by the user), to receive more user data from some softwares, etc.

These future OS will target the user life as a whole, aiming to help the user to have a better life. E.g., a good balance in activities like work, recreation, health, sports, etc.

It would be a next (or next-next) generation OS, called "Life OS" or "Personal OS" or similar.