On one of the more recent episodes of ATP they were discussing the report from Apples latest earnings that iPad sales are continuing to fall. They are not the the only ones to mention it either as Recode and Business Insider as well as other news sites have mentines the decline in Apples tablet.
There is much speculation across the punditry on why this is happening (lack of ability for a tablet to do real work, bigger phones have more portability than a tablet with a big enough screen for movies, reading etc).
From peronal experience, I can say that my tablet is several years old and still runs great so I have intention of upgrading in the near future. It is a complementary device to my Mac and iPhone that I use it for consuming media while reading or watching a video. The tablet could not replace my laptop in terms of power or computing flexibility nor my phone in terms of mobilty (and camera). I enjoy my tablet greatly though I can understand greatly while sales have slumped (though by no means are the sales bad; it is just compared to the rarefied sales of the iPhone it is hard to not see the differential.