In my mind, you're talking more of a smartphone than a desktop, these are pocket-sized, portable, pre-built devices. Not 2 foot tall, 8 inch wide machines rooted in one spot. With decreased size comes decreased customizability.
Speaking as an electrical engineer, you probably are soldering the darn thing together at that point. And probably having to custom-make your own case, I doubt people who make money selling over-the-counter super-smartphones are going to make generic cases terribly prevalent.
This is why the numbers I gave are for how I'd probably handle it. My view, putting together a smartphone-sized complex computing device is not cheap, easy, or plausible for most people. hot-swap circuitry only gets so small before you hit the thermal-breakdown points, &c.
It is 2072, I'm sure they've made some advancements (though I can't tell a difference between my droidX and the stats for a Transys Avalon running Novatech Navi*), so I wouldn't scream if someone running a game told me that I could purchase pre-fabbed modules for building my own comm-link, along with a generic case and power supply to host it all in, it just doesn't fit my style or knowledge base.
* Before anyone gets started on AR, VR, etc, need I remind you those are accessories and network protocols, not the core commlink/smartphone technology. In fact, since we're talking about the droidX the primary ad-hoc wireless networking component is in there.