It's worth noting that desktop computing is being relegated to the groups that you mentioned only because they are the only groups remaining that have a compell

It's worth noting that desktop computing is being relegated to the groups that you mentioned only because they are the only groups remaining that have a compelling use for a full-sized desktop, not because of some innate laws of the universe. It's at least partially on Microsoft to come up with good reasons for normal people to use their platform over all other options, and they've fallen very flat on that note in the past 15 or so years - particularly in the consumer space. It'd be interesting to see a revitalized Microsoft really attacking this space, but the promotion of Nadella makes me think that this isn't really what the MS board has in mind.