Prediction: Apple is going to move away from the notion of Hard Disks for their consumer-oriented mobile devices. The Flash chips in SSDs are already somewhat like dynamic RAM, though not quite as fast and with some extra requirements and limitations. One could easily give the illusion of a laptop with 256 Gigabytes of orthogonally persistent RAM by using 8 Gigs or so of dynamic RAM as a cache into Flash RAM. No need for any notion of a separate persistent store like a Hard Drive. No need to even boot up! Laptops would only have "hibernate" and "sleep". (You'd need ECC, wear leveling, and ways of transparently "retiring" sections of Flash RAM that go bad.)
Go one step further, and use the cloud as a backing store with an always-on mobile broadband connection. The 256 Gigabytes of Flash RAM would act as a local cache to cloud storage.
What do you mean "already started doing it?" Please point out the OS X or iOS device whose kernel has no notion of a "Hard Disk" or something like it. With what I'm talking about, the kernel would see nothing but RAM.
As far as I can see, they just started doing away with the case of the hard drive mechanism in their laptops. As far as even their iOS devices go, they still have a notion of a separate persistent store with high latency characteristics completely separate from a non-persistent RAM.
What I'm talking about doing is making dynamic RAM, Flash RAM, and the cloud all just a part of the memory hierarchy with orthogonal persistence.
This is going to entail a lot of engineering which isn't yet in evidence in any of their current products. Such devices would never have to boot-up! I'm not sure such devices would be capable of being booted up. They'd also need more sophisticated error correction than current devices have. (Current devices can just correct the rare memory corruption event by being rebooted.)
Go one step further, and use the cloud as a backing store with an always-on mobile broadband connection. The 256 Gigabytes of Flash RAM would act as a local cache to cloud storage.