I forsee Apple and Google (and Microsoft?) devices will increasingly be aimed solely at consuming content. This will be the "interactive television" of the future.
If you haven't noticed, it is not easy is it to turn an iPad into a router/server. Perhaps it was not meant to be. It is an "interactive TV", for sharing and consuming content. These type of devices are not under the control of users; they are ultimatly controlled by large corporate interests, in the same way that TV is the medium of government and large corporations. That is not "revolutionary", just business as usual.
As such, I posit that it is another computer -- the computer that retrieves data from the internet and sends the content to your TV-like device -- that is the most interesting, and hence the most "revolutionary". That is your router/server.
The OP, a programmer, calls it "one of [his] best hacks."
This I believe is the "PC" of the future. The "PC" was at one time a revolutionary device that brought the power of computers, once reserved only for those who could purchase and administer mainframes, to the home and business. Where would Apple, Google if not for the PC revolution?
I believe the home router/server (not your beautiful form factor, high priced device) is, going forward, the "PC" of the future. This is the device that you can program for free, that can run open source software, including an open source OS of your choice, that you the user can fully control, and where real innovation can occur. This is where the "PC revolution" can continue.
The OP says he does not see why there should be a separation between programming and administration (e.g., a subset of programming that, allong with basic networking know-how, allows the user to install and configure her own "server" at home).
As a user, if I could only master one and had to choose between the two, I'd pick administration over programming. This is because I feel it is more useful to me as a user (like the OP, "one of my best hacks"). As such, I am biased toward administration and believe if there is to be another "PC revolution" I believe it should be focused on the home server/router and, if so, must be lead by those who can at least administer computers performing these crucial functions.
The only PC of the future I can see is what would be considered an embedded system of some description at the moment; not a re-purposed one but one that is designed to be used for something else.
I don't see ARM or Intel getting a look in here as they are not open architectures. ARM is almost always in a notoriously unknown licensing status from experience.
I reckon that the market will divide into consumption, some open architecture that doesn't exist yet (for power users, enthusiasts running Linux) and this sector which is hacking devices.
The PC of the future doesn't exist. Yet.
It is the evolution of "development board".
It is the "home computer kit" in the back of Popular Science that started the PC revolution, but this time much, much easier. Because we have heaps of free software.
As another comment suggested, hardware has been commoditized. It follows that system software will also be commoditized.
Sure the techie types will always want to get into the nitty-gritty, but my mom can't even set up a router, let-alone program it.
I think the future is cloud-based (ugh, buzzwords, but true) services like IFTTT (https://ifttt.com/) that let non-technical users manipulate content/events without touching code.
When every device in your home is connected to a public network, I imagine that you, a techie type, are going to want some control over what and how those devices communicate with the public network.
That control will not likely come through the device (at least, not easily, anyway). However it could come through your router/server.
Not really, there were other platforms already.
What PC brought was commoditization of hardware instead of proprietary extensions used by other competing home computers.
It doesn't use much more power than the linked NAS device, but comes with basically the same hardware as the Nexus 4, on a nice board with all those useful connectors. Quad-core 1.5 Ghz CPU, 2GB of RAM, SATA and Gigabit ethernet.
There's a small community forming around the board, so there's some degree of support available. But currently it's not comparable to what's available for the Raspberry PI, you still need decent linux skills to set it up. But that's half the fun anyways.
I've been looking for something to replace my Dreamplug for a while and this might do it
On a side note, for the newer (not the newest) edition of the WD My Book Live (and its 2-disk brother My Book Live Duo) NAS device, the OS is a full-featured Debian already, and you can easily enable SSH to login and `apt-get` almost everything you want. The processor is a MIPS one, though, not an ARM one, which might affect the availability of Debian packages. However, I've heard the newest edition called WD My Cloud NAS runs on an dual-core ARM processors.
People who are less hardware-hack-oriented (like myself) should definitely give those a try.
Any ideas of boards with gigabit ethernet?
I have one. Great specs, but I am not totally happy with the ubuntu 12.04 that comes with it. GCC is broken, for one thing: http://www.utilite-computer.com/forum/viewtopic.php?f=64&t=1.... Hoping this gets fixed soon.
The OP is "sharing media files with Samba to an Android tablet", but if you really need >100mbit to do that, I don't know what to tell you. I'm puzzled by everyone that wants to grind every random cheap SoC into a media server.
You don't have to hack it too much in order to get a 'full' linux on there. You can enable SSH access on the system via the web UI. From there, you can set up a simple packaging system to install most other common binaries (and a functioning build environment to add anything else)
Take a look at: http://mybookworld.wikidot.com/optware for instructions.
If you are interested in this space, join the Amahi community! People interested in building hardware are especially welcome https://www.amahi.org
Edit: one person asked how to join - there's the forums and there are the github repos to contribute. There is also the developer mailing list
It also has a number of GPIO pins, UART, i2c and SPI, which may be of interest to those who do own soldering irons :)
 A model with no Ethernet is available for $25, but Ethernet is kind of non-optional for a server :)
 The price doesn't include power supply, case or boot media.
I had a plug-computer before they were cool (the Globalscale Dreamplug) and it's been pretty good for almost 3 years now.
Less headache (though not as fun!), more storage space, less latency, more processing power at a still very low power consumption :-)