The last successful launch of a &quot;new&quot; operating system was maybe iOS? Whereas there are plenty of expensively developed commercial failures littering the path.<p>A serious problem: who would pay for the development of a new OS, or sink a very large chunk of free time into it? What properties would it have that could not be achieved starting from one of the POSIX OSs? Who would port all the apps? Why would people - end users - adopt it?