It should be pretty well known by now that upgradable components in hand-held devices is a losing strategy. The mass populace of Consumers just don't care, they wan't something that Just Works, that's simple, pretty and light with a long battery life. Which appears to align with Apple's focus perfectly.
I think it's safe to assume that iOS devices aren't going to come with upgradeable internal components. They've got models at different price points and their 3rd party hardware ecosystems - which they plan satisfying the consumers use-cases until the next version rolls around again.
It may take YOU 20 seconds. It takes my mother upwards of five minutes to replace the batteries in a standard D-cell flashlight, and then another five minutes to do it all again because she didn't put all the batteries in in the same direction.
People really appreciate things they don't have to fuss with.
What if it was so much cheaper and not subsidized, like how desktops are? It could have been a different type of market, and maybe better for electronics altogether. That's how desktops were, anyhow. And the internet. Phones are getting to be like cages, though.
I think it's safe to assume that iOS devices aren't going to come with upgradeable internal components. They've got models at different price points and their 3rd party hardware ecosystems - which they plan satisfying the consumers use-cases until the next version rolls around again.