The market tends not to ignore 80% dominance for long. (You can debate just how dominant Android is in various countries. Here are some market share charts. But there is broad agreement that Android has more users in than Apple in huge stretches of the world.)
But Apple fans ought to worry that Cook has a mistaken view of how powerful Android is. Android phones particularly the high-end ones can do 95% of what iPhones can do, at a fraction of the cost. There is a good chance that many of those users are simply never going to convert to Apple, for the same reason that Ford drivers never convert to Rolls Royce. Sure, a Rolls is nicer than a Ford. But both get from A to B equally fast, and the Ford does it cheaper.
This goes to the core of Apple's growth problem. Growth has halted in North America, yet Apple does not see Android as a threat.