I don't think this will become widespread. As an employer, I don't want to have to support a variety of hardware/software/OS combinations which might be provide

I don't think this will become widespread. As an employer, I don't want to have to support a variety of hardware/software/OS combinations which might be provided by employees; I don't want to depend on employees to maintain their equipment appropriately; and I don't want to create a circumstance where my data is sitting on hardware I don't own, especially if the owner is someone I've just fired or who's just been hired by a competitor. The cost of a computer or a cellphone is tiny next to the cost of an employee - I really don't see much win in this idea for anything but tiny companies or a few isolated examples.