In business, increasing your share of a shrinking market can be very concerning. If all Apple sold were iPads it would be more than worrisome. But in this instance I think this is good for Apple because there will be substantial tablet market for many years. 35 billion, give or take, in revenue per year is nothing to scoff at. And a shrinking market could cause departures from some tablet makers freeing up the ability to gain more share.
The best tablets are ipads. If ipads are proliferating more throughout the tablet market, that’s a win for Apple.