In the era of Blackberries, corporate email (although important) didn’t add value to the device enough to make the user care deeply for the device. Jumping forward a decade, the fact the corporate provided device now has family pictures and an individuals music collection, the value of the device to the individual has risen significantly, to the point where a user will spend his/her own money to personalise and protect the device.
More and more users purchase cases for their corporate approved device and the complex (for the average user) of switching handsets makes upgrading time consuming and tedious. The fact a case has been added to protect the device (that contains family photo’s) also means handsets are better protect and less likely to be damaged.
So I can see handset refresh cycles slowing as users hang on to their devices for longer which will be a double edged sword for the enterprise. Less spend on hardware, but it becomes harder to maintain an up to date fleet running the right level of secure firmware.