I disagree 98.5%
Slowdown of sales growth doesn't prove your previous conjecture, nor your current supposition. It just means that the need has been fulfilled, not that the need is going away. Once most everybody that wants a tablet has one, they don't need to keep buying them. We're depleting the pool of people that want one and don't have one, nothing more nothing less. And as everyone gets sufficient value out of the tablet they have, they'll buy a new one, shinier, prettier, lighter, faster, better graphics and sound, cooler apps, longer lasting batteries, cooler cases, hopefully more external interfaces, and new whizbang features. I'll never be able to read books and PDF whitepapers on an iPad, and I hate pulling out the laptop. So tablets fill a major need in terms of form factor. And if you think I'm going to buy, use, or store in my pocket a "phablet" well you've just jumped the shark to crazy-land. They're OK for people that can't afford an iPhone or iPad, or don't mind looking stupid (like everyone did with a contact manager back in the day, and the way Palm Pilot people still should feel) using and talking into some monstrosity of a phone. But the "installed base" of tablet users are still there, and happy using a logical form factor, rather than a "tweener" more adept at marketing to and satisfying cost-sensitive users. My prediction, years from now I'll still be using an iPhone, an iPad, and a Macbook. And no, it won't have voice recognition--enven if it does I won't use it--or mind control, or an interface with my glasses. And you said it yourself: "The phone is just big enough for reading ebooks, emagazines, and Web surfing comfortably. The tablet still provides a better experience for those activities, but it's not essential." In other words, phablets are just a way of making do. They're "almost" useful, and they're just a "tad" smaller. A tweener solution, some will like it, some will stick their noses up at it. But it's not putting tablets out of business anytime soon. If anything, you'll see iPads gradually replaced with Minis and new form factors that try to find the perfect mix of form, fit, and function. It won't be a phablet though. And if the Mini comes out with a 4G phone capability, bye-bye phablets. People will still need their iPhone, though, because a mini will never fit in our pockets.