As an aside to the thread about windows7 launch which received so many posts i think it should be asked 'what is an operating system'? i.e. when there is discussion over copying of ideas, and who came first and which is best i think it should be said that surely there is a common or natural end goal of operating system design, working in a similar way to evolution where changes and 'improvements' and 'environmental pressures' are pushing a design envelope which at some unknowable, unreachable point will create a perfect user interface.
Now clearly we are seeing more convergence in the available products despite who thought of what first they are bound to become more similar as 'evoultion' gets closer to the design ideal, they will all be providing a very similar optimal solution to the given problem.
If we were to say for example that moores law had been borne out and little further technological development could take place (silicone based etc) ask 'how much innovation is left?' given that the operating systems would not suddenly have to deal with supporting a teleportation device or new hologram internet conferencing etc.
I believe that as with other industries, with so many high quality products all offering and able to offer the solutions required by the end user that it will simply come down to aesthetics and preference, "i like the big bubbly icons", i like the sharp edgy ones and snap screen effects blah blah"
What is an operating system? an interface that lets us make use of the operations that a computer can do for us in an easy way, without which 99% of the worlds population could never use a computer to do anything. Have we not already reached as useful and easy to use as an operating system can get, if technology were not to place more demands, will and should the main advances be in our 'hard' interface with the OS? would people want to use other interfaces like being able to speak in any old way to your machine and have it understand, a la star trek computer? would people like an interface similar to the one in that Tom cruise movie were you pick and move items on a virtual screen, but then do you not just become a glorified mouse?