I once worked with a forward thinking executive that predicted this shift: This was over 20 years ago.
It's probably hardware miniaturisation and performance that's held back the shift. Now that we hold a powerful computer in our phone handsets, our lives and businesses are considerably more portable.
Steve Ballmer's Letter to Microsoft shareholders.
"Last year in this letter I said that over time, the full value of our software will be seen and felt in how people use devices and services at work and in their personal lives. This is a significant shift, both in what we do and how we see ourselves — as a devices and services company. It impacts how we run the company, how we develop new experiences, and how we take products to market for both consumers and businesses. The work we have accomplished in the past year and the roadmap in front of us brings this to life."Steve Ballmer's Letter to Microsoft shareholders [microsoft.com]
Put cynically, Microsoft is apparently copying Apple again. But this letter only formalizes a transition the company has been making for years. And unlike Apple, Microsoft will continue to partner with hardware companies more often than making its own devices. As with its core new product, Windows 8, Microsoft is in that way a hybrid, one that serves a more diverse audience than does Apple.