http://www.computerworld.com/article/2908957/is-your-business-ready-for-stick-pcs.html
http://www.computerworld.com/article/2489541/cloud-computing/review--dell-wyse-delivers-android-on-a-stick.html
http://www.computerworld.com/article/2913375/computer-hardware/review-the-intel-compute-stick-the-ultimate-mobile-pc.html
http://www.computerworld.com/article/2904441/google-tries-sticking-it-to-microsoft-with-chromebit-announcement-itbwgk.html
Here in the United States there are three PC's on HDMI sticks that are coming out you have Ubuntu and Microsoft with a deal with Intel doing Intel Compute Stick.
Google's Android Division and Dell have Wyse Cloud Connet for its HDMI PC Stick and
Google's Chrome OS Division has a deal with Asus for the Chrome bit.
nope
Yes. They've been around for a couple years in form of Google Chromecast and Amazon Fire TV (though neither are as sophisticated as what is being proposed at your links, bing).
Yes, I have never tried Chromecast, but I have a Fire TV stick and love it. It's works better and has a better interface than Roku.
As for stick PCs, sort of. I searched on Amazon and saw several models. In that same search, however, I saw this (http://store.hp.com/webapp/wcs/stores/servlet/us/en/hp-stream-mini-desktop---200-010-p-k5g59aa-aba--1?srccode=cii_23393768&cpncode=43-47440165-2&jumpid=ba_r329_hhocse&aoid=41841&003=6571619&010=K5G59AA%2523ABA#!&TabName=features), a mini PC that is not a stick but still at a good price. I think it is a better value because it is upgradeable. It comes with a 32GB Solid State drive. That's not much, but it's more than enough to hold Windows OS, and with so many USB 3.0 ports it is no trouble to add more space. The RAM also needs a serious upgrade, but that is also easy and fairly cheap using notebook RAM. It's not a stick, but better I think. It is still small enough to easily hide behind the TV. I'm loving this little thing; it's fast and capable!
If you buy this machine, be sure you also order a bluetooth keyboard with touchpad. The keyboard and mouse included are not wireless.