I'm not sure why there is always an obsession with 'growing' sales.
The iPad isn't something you need to constantly replace. I have the Air, I'm not willing to spend $600 or so to get the Air 2 just so it will go slightly faster and have the Touch ID.
I'm sure I am among millions of happy iPad owners who are not going to rush out out buy every new version that comes out.
I'm fairly certain Tim Cook said that is a Wall Street obsession of constantly growing iPad sales. Wall Street is run by a bunch of greedy jackasses. Any one with any common sense would realize Apple's profit margins are higher if they sell larger iPhones in place of iPads. So why should Tim Cook and Apple get all bent out of shape if iPad sales are declining. It's not as if consumers are dumping their older iPads for new Android or Windows tablets. They're simply holding on to their older iPads which are still useful to them. It's Wall Street that believes Apple should be able to sell all of its products in equally high numbers which I say is fairly impossible. I don't think every consumer needs every product in the Apple lineup and definitely not multiples of the same product. That's just Wall Street greed gone wild.
I believe there are a finite number of consumers who NEED tablets and eventually sales decline will stabilize. I'm not sure who is stupid enough to think that sales of all products grow indefinitely, even in theory. Right now there's large-display smartphone growth and in time iPad sales may start to increase again. What's the big hurry? Consumers can't or shouldn't be forced to just keep spending money on products they don't really need. That's not necessarily Apple's fault although some people think it is.
I'd thought Apple would be able to greatly increase iPad sales through educational institution means, but that seems to be at a dead end. I guess schools are going with computers using physical keyboards instead of tablets with their virtual keyboards.