I just did a quick hunt around the internets, trying to figure out prices for, say Micro SD cards at the different capacities...
16GB = $10-15
32GB = $20-25
64GB = $50-60
but not seeing any 128GB micro SD cards. (Not that they're using micro sd cards in the iPhone, but just trying to get a picture in my head of what the storage chips cost...)
So it's not in the iPhone because:
- it exists and it's too expensive,
- it doesn't exist
- it exists but isn't proven enough for Apple to use it...
- or [INSERT REASON HERE].
So, I kept hunting... Found a story from June (yeah, I know it's september now, but the phones have been in production for a little while, no?) regarding 128GB chips/phones, saying that SanDisk is "still working on 128GB" storage.
SanDisk product marketing manager Ruben Dennenwaldt said that micro-storage capacity of “128GB is certainly something we’re working on”, and that the technology needed to produce 128GB phones will “absolutely” be readily available within the next two years. Although vague about exactly when the prerequisite tech will arrive, Dennenwaldt says SanDisk is “making very good progress in the next capacity point.” Full-size 128GB SD cards are already available – Sandisk’s own 128GB Extreme SD card sells for just over £100 – but getting the size down to a level that will fit into microSD cards and today’s slim phones is “a significant challenge.” Dennenwaldt explains, “for microSD, from a technology perspective, the maximum that can be done at this point is 64GB, purely because of the form factor.”
http://www.trustedreviews.com/news/128gb-phone-tech-is-coming-says-sandisk
So, my feeble guess is that at some point in the next six months they'll bump up the storage on the iPhone 5S. (Maybe piggybacking on the announcement of some other new thing.)
Or it simply arrives with the next iPhone, a year from now.
Sure, it would have been nice to have Apple say why they couldn't/didn't offer a 128GB phone, even if they just added it for another $100 (instead of bumping up the whole line)... But I know that's not their style to apologize for or justify shortcomings or unmet expectations from the rumor-mill.
I'm starting to think that, if 128GB were available (or cost-effective enough to at least offer it), they would have touted it.