Re: iPads caught in a trap
"iPads do seem trapped -- can't go bigger, can't go smaller -- and users will feel that redundancy."
I don't think iPads are caught in any trap. In fact, I think the sequence in size: iPhone 6, iPhone 6 Plus, iPad mini, and iPad Air is perfect and couldn't be better. If I were Apple, what I would do next is take the MacBook Air, which is a great device, and make it with a detachable keyboard.
"Once I bought the Galaxy S5 my Nexus 7 tablet has spent a lot more time on the bench. I basically use it to read Kindle books and not much else."
How you use a device is one of the main reasons --if not the most important-- to consider when choosing a new one. You always have to ask yourself what your needs are. For someone who already uses an iPad Air, or any previous iPad for more than reading books or browse the Web the size of the iPad Air is just fine. When you add a good iPad keyboad (there are some really good out there) you can get a very nice MacBook Pro mini sort of thing. It's perfect if you do a lot of writing.
I know someone who does a lot of writing on his iPad. Not long ago he said maybe the iPad mini would have been better, as it's smaller and he could still do his writing. Much also depends on the individual's preferences and needs.
I have an iPad Air. The size is perfect. I do some writing on it and use the touchscreen keyboard, which works very well. I prefer tablets to phones, which means I am not the person who would upgrade her phone too often. However, I see the iPhone 6 Plus attractive because of the bigger screen. Which one would I choose between iPhone 6 Plus and iPad mini? I don't know yet.
If I would have to choose between the iPhone 6 and 6 Plus I choose the iPhone 6 Plus, probably because of what I said above about me not being a phone addict. I spent almost two years without carrying or using a phone as an experiment. :) Great insight I got, not to mention the freedom of being unreachable when I wanted.
As for OS, I love Apple's OS X and iOS and wouldn't change them for anything else simply because Apple has the best OSs. :) So, as Michael was saying, the iOS 8 is going to be important when people decide what tablet or phone to buy next. It's a combination of hardware and software what makes a device what it is, I believe.