I guess 4K could have a good reason to have more storage, but this a phone.
What do we do with video ? we never leave it on there...
1. We shoot
2. We upload..
3. We delete.
4. We get hits on Youtube
More storage would just mean we could have multiple 4K video. That's pretty much the only reason. There is nothing else that i can think of that would need allot of storage, we can't do now, expect just "more storage for ....." ???
I would expect the 256GB iPhone to be inevitable. But let's look at the evidence so far:
The iPhone can now shoot 4K video
It can take 12MP photos
It can take Live Photos
The camera connection kit just became compatible with the the iPhone in current models.
The iPad Pro Lightning connector can support USB 3.0 file transfer rates.
Now why would Apple do all of these things? Clearly it's to allow media content created on the iPhone to be offloaded efficiently. While the camera kit can be used to get media onto the phone, it's not an easy task, so that seems less likely. But that could change in order to take 4K movies on an iPhone and import it into the iPad Pro -- though like the iPad and camera kit in the past, that capability could be restricted to the iPP.
Now we have a rumor that Apple may be preparing to accommodate HQ audio files, which will add considerably to the local storage. And most recently the rumor of 256GB storage on the iPhone 7, which would go along way to accommodating the extra file size of both video and audio -- why else would they offer it with the 7 and not with the 6S, unless the 7 users may really need it over the 6S users for whom it would just be helpful?
Apple has long said the iPhone doesn't need more storage because iCloud can stream all of a users content, whenever needed. But iCloud is useless for creating HQ content, especially when you're on a family vacation at Machu Picchu, shooting 4K movies with HQ audio, 12mp photos, Live Photos, and panoramas; and there is no internet available. That 128gb, or even 256gb is going to run out fast, especially if you've got a lot of apps on there -- games in particular can be huge. In which case all of these other recent implementations come into play, and sticking your camera kit into the iPhone and quickly offloading photos and videos onto 64GB SD cards would come in very handy.
And frankly, I don't believe there's going to be much Hi-Res commercial audio or video for streaming and download anyway. So all of these rumors are adding up NOT to be about that, but the user created content. Pro video AND pro audio. Later, Apple can get into content with the foundation laid for it.
Moreover, whether Apple removes the 3.5mm Jack with the iP7, or ever, is irrelevant to these rumors, but certainly makes them more compelling as that rumor, along with the rumor of manufacturers gearing up their Lightning audio products, suggest that taken as a whole, that the iPhone 7 is going to need expanded offline storage for larger file sizes which can be created with the hardware. Whether an "audiophile" wants to store large audio files, or a movie buff wants to store large movie files is a secondary perk. And the USB 3 speeds guarantee the bandwidth is there to pass huge data streams in realtime from all this new Lightning audio equipment rumored may in the works.