There's really only one way to respond to this:
Anyone who bets against size reduction for the computers have not been paying attention the last 60 years.
Devices that integrate a screen may grow in size to accommodate the screen size in some cases, but all else keep shrinking.
We used to have full towers in computer stores. Now mainstream electronics stores often don't even sell computers in small ATX cases; a substantial number of the models come "baked in" to monitors, and there's a rapidly growing market for "TV sticks" that are basically Linux/Android ARM computers the size of credit cards or less, that you plug directly into your HDMI slot on your TV/monitor with no cable, and more and more mobile devices supports MHL or other ways of wirelessly mirroring the screen.
Meanwhile the desktop market as a whole is stagnant, and the laptop market isn't doing much better.
There is basically no reason to assume that these trends won't continue:
* Devices will get smaller, as capability per square cm grows faster than most users needs.
* Devices will increasingly be wireless; even many desktops these days use wireless keyboards and mice, and alternatives for wireless connection to screens are becoming more and more common.
* Mobile devices will get more features of typical desktops as their performance and capacity increases, and wireless connectivity improves. You can already install apps that let you run full Linux desktops on most Android devices, exporting the display over the network via VNC etc., and you can expect that with things like Miracast those capabilities will improve.
It will not take long before the typical mobile sized device is as fast as what typical users expects of desktops and laptops - a large part of the reason the desktop and laptop market is stagnating is that people are not replacing them very often any more, as they are "fast enough" for most users. When mobile sized devices are fast enough, and wireless display and input support is good enough, there's very little reason for most users to want a typical "PC" device, over a range of variations from the "TV stick" to mobile devices that connect wirelessly to their TV or "laptop shells", or over tablets with docks.
So while not all of us will use our tablets or phones as our main computing device, you should expect size of the "computing element" whether embedded in a larger device or standalone, for mainstream users, to keep shrinking, and you should expect to not need a cable to it other than for power.
Of course there will be exceptions. There will always be people who need more than average for whatever reason (says the guy with a 15 drive slot Lian Li tower case under the stairs). But that will be fringe uses.
