Will Credit Card Sized Boards Take Over The Traditional PCs ?

I don't think desktop PC would ever be replaced with anything else. In terms of desktops or workstations, the users aren't that concerned about the size but their performance. The CPU size may go down, but we would need desktop screens due to the many interfaces we need to be working on, in terms of video editing, military or other domains.

In terms of computing power and size, we already have smartphones and tablets going smaller and better day by day. Also with the dawn of smart watches, I guess credit sized boards is a possibility soon.

It may happen,but not so soon! Even the people buying desktops for gaming are not going to throw those right away!!😉

Smaller the better. But that's not it. We've to look past a lot of things.
Even today, a lot of professionals struggle to afford computing systems and for them Raspberry Pi might be the ideal solution. At a price as cheap as $35, when one can buy the power supply or an SD card separately at a low cost, what Raspberry Pi just needs is a just attention.

A light version of Linux and open-source software for spreadsheets, word processing, and other common applications is already there and unlike traditional operating systems, the Raspberry Pi does not require a large amount of memory. In fact, the Model A has 256MB of RAM, while the Model B has 512 MB of RAM. In comparison, newer versions of Windows can take up to 4GB to run at optimal speeds.

The device also comes with USB ports, an Ethernet port, so you can connect external devices and use an Internet connection, an HDMI port, video port, SD card slot, audio jack, and a footprint for a camera connection.

It pretty much covers up everything you need from a PC. And covers such little space! Doesn't that make you wonder, whether that is where lies the next big disruption?

The best feature of all in Raspberry Pi is "GP I/O ports" which you can connect your self-made circuit to RPi & use RPi to control your connected devices & receive+interpret signals using it.

Abhijit Dey

The CPU size may go down, but we would need desktop screens due to the many interfaces we need to be working on, in terms of video editing, military or other domains.

Here we are discussing about Boards taking over "PCs - Personal Computers" & not boards as replacement to Military Computers or Servers or Workstations.

Anyways,
From what I know Raspberry Pi,Beaglebone & UDOO are capable of doing everything that can be done in "Normal PCs" (like surfing,coding,accessing documents etc.) & Even more than that using GPIO Ports which our PCs lack.(UDOO is still UD though)

Computers used to have "GP IO ports" aka serial ports. But users felt it was slow and subsequently got outdated. Now it's making a comeback!! If people were happy with the speed of RPi configuration, they wouldn't be asking for quad and octa cores in phones (not only PCs).

The point is there will never be a single device which will replace everything else. Always use the right tool for the right job.