Nobody operates in a vacuum. Not that they're slacking, but I'd love it if someone leapfrogged Apple in the UI area. Competition is a very good thing.
There isn't much competition in a oligopoly. You are not going to see any innovation from any new companies . The barriers to entry would be extremely high and the market share is already dominated by a few companies. Hopefully companies like Apple and MS continue to use their sub-normal profits to innovate.