Is this the new icon theme for Ubuntu 12.04? http://www.yellowicon.com/portfolio/icons/ubuntu
Canonical shows up on the Yellowicon clients list. http://www.yellowicon.com/clients
I do not know whether this icon set will be selected. In general, things like icon set, background image and so on are finalised closer to the release date, about a couple of months before the release.
No. Those icons were designed by Yellowicon at one point for the then-upcoming Ubuntu 10.04 LTS release. But from what I understand, when one of the main designers for the theme left the company for Apple, work on the theme was cancelled.
Ubuntu 12.04 LTS still uses the Humanity icon theme.
If you wanted an idea of how the theme might have ended up looking on your desktop, however, you could try taking a look at FS Icons Ubuntu, which is a third-party icon theme inspired by the cancelled Yellowicons design. It can be downloaded from either gnome-look.org or deviantART.