In line with my five-year prediction of the end of the user-visible filesystem, the way data is stored on the iOS is completely invisible to the end user. Every application has its own storage area, the contents of which it can present to the user in any way it chooses fit. In particular, you do not find explicit "Save Document" buttons on these apps anymore. Every time you connect to iTunes, everything gets backed up, when you move to a different device, all data moves with you, and since the applications are isolated from each-other (and the operating system) this approach also has immense security benefits.

However, the current situation is only the first half of the solution: It works great in that applications can let the user focus on what he needs to do, rather than having to worry about what files to store his documents in. But it decidedly falls short when trying to work on the same data with multiple applications, devices and/or people. Apple does not really have a good solution for this, but someone else stepped up to the plate, at that is Dropbox.

Dropbox offers a cloud storage service, which allows their users to access files from all their computers, and even a web browser. They can also share files with other people. What made Dropbox so popular is that their client software is very good at managing the underlying complexity: The Dropbox folder appears just like any other (shared) folder on your computer, all the data transfer happens automatically in the background.

Dropbox also had the foresight to offer a developer SDK for iOS and Android, has seen a flood of applications integrating the service, to the extent that, especially on iOS, Dropbox has become the de-facto standard for sharing data over the cloud. Before that, people often resorted to sending things by mail, even between apps. Apple has a similar service (MobileMe), but has completely missed the boat on this (I think Google is doing better in that area with Android).

Here is my prediction:

• iOS 5 will contain a new feature Shared Storage Area (it will have a cooler name, though).
• You can set how many GB you want to allocate for it, and that much space will be reserved on your device. You can resize later at any time.
• All apps can read and write files in the Storage Area. It is intended for sharing data (not for application-managed files), so the UI will be just like the current Send to Dropbox (or Print).
• Apps that want to use the Storage Area will need to ask you for permission, just like they do now to use the GPS or notifications. This is important for security. It could be fine-grained (read-only, and on a per-folder basis), but I think to keep it simple it will just be on/off.
• The Shared Storage Area is also replicated (as a folder) on your computer, so you can open and update files there as well. It will be synchronized when you connect to iTunes.
• If you happen to have MobileMe, there will be over-the-air synchronization with your MobileMe storage.
• Dropbox will integrate this into their iOS app as well, so it will also synchronize with your Dropbox account.
• The important new piece that Shared Storage has over Dropbox is that apps on the same device can share data fast and offline (because they can see the changes made to the locally reserved area immediately, without any network overhead).

The only reason I can see for Apple not wanting to do this is that it is too obvious. But the need is there, and they will have to implement it, even if it is in the obvious way, just like they eventually did with copy/paste and printing.

And my hope is that Apple does this without buying Dropbox. Don't want to see the same thing happen to Dropbox that happened to drop.io. The MobileMe integration should be optional and open to substitution.