I am not sure where the author is getting the idea that these 3 companies "have generated most of the new ideas". Business momentum I can see, they had the brands, marketing department, and resources to get things out into the public sphere... but most of the new idea? Not by a long shot.
I do not accuse their engineers of sitting on their hands, they came up with some good stuff, but the bulk of the 'new ideas' tends to come from small companies, FOSS projects, research, and students screwing around. A lot of the ideas put out by those people are also crap, but then again a lot of the stuff coming out of the those big three are also pretty bad, even the ones that see the light of day.
I would say if anything it is the marketing departments and executive structures that are 'running out of steam'. As a company matures it tends to get entrenched people who have been there a while and are more interested in a steady return then experimentation and, more importantly, the companies tend to hire more and more 'classical' executives from other industries who are great at investor retaliations but tend to push the company into the 'endless sequels, people like what they have seen before!' direction.