It's not just the iPad - the entire tablet market is in decline
It's not just Apple's iPad that's in trouble. The entire tablet market is in decline.
Statista put together this chart based on numbers from IDC. In each of the last four quarters, tablet sales have been down from the previous year's quarter. Overall, shipments in the first three quarters of 2015 are down 9% from the same time a year ago.
What's going on? Apple started making larger phones, the iPhone 6S and 6S Plus, a year ago, which eliminates some of the justification for a bigger touch screen device. Also, consumers upgrade their phones every two or three years, since the carriers subsidize some of that up-front cost (plus, it's just cool to have a new phone, which you carry with you everywhere in public). Tablets are more like PCs - you buy a new one only when the old one is worn out or doesn't run the software you need.