I don't think he was saying that they will keep making the same products forever, it's that their core values aren't going to change, as they shouldn't. It's in the companies nature to experiment in new products, and that is what is not going to change.
"...in history’s rear-view, his biggest achievement will be having ripped music retailing out of the labels’ hands, and mobile software out of the telephone companies."
Those are great achievements, but Apple II? Lisa/Mac? Pixar? Rescuing a failing company and bringing it from oblivion to the most valuable company in the world in only 14 years?