@araknoid
Excuse me if you already know, but since you're new, you might have missed that today there are two competing solutions (in development).
One is "AmigaOS4" which components are currently developed by Hyperion mainly on Classic-Amigas with the PPC-boards from the former Phase5.
It's intended to run on the so-called "AmigaOne" later, distributed by Eyetech, who simply resell a reference-design PPC-board by the northbridge-manufacturer MAI called "Teron". You could buy some of these Terons/AmigaOnes already, but currently the more appropiate name would rather be "LinuxOne", since OS4 is not ready yet. In fact, at least very few weeks ago it had not even all components integrated together yet (especially a key part, the emulation, is missing), so that it's not even in real betatest yet (just it's components for itself).
The current "Amiga Inc." (since 2000) plays, as in the years before, no major role in all this, they just gave licenses for the use of the trademarks and the source-code of AmigaOS 3.1 (the source-code for 3.5 & 3.9 is owned by Haage&Partner who developed those updates back then). Hyperion have even to acquire the money for the OS-development themselves, so OS4 is basically their's but might be bought back by AI later.
On the other hand there is
Genesi, who's key developers (HW&SW) are from the former Phase5- and CGFX-RTG-teams, i.e. among others the guys who brought the first and only PPC-CPU-boards to the 68k-Amigas.
Genesi have developed their own PPC-board called Pegasos, which does have a few additional features compared to the Teron and is smaller (microATX).
Furthermore they've developed their own, AmigaOS-compatible OS called MorphOS. MorphOS is already even in public betatest for many, many monthes. Both, Pegasos and MorphOS, can be bought by plain end-users for some time already - although just in limited quantities yet because of continued delivery-shortfalls of the northbridge-manufacturer Mai (see above).
Therefore Genesi got fed up with them and cancelled the Pegasos-I in favour of the currently developed Pegasos-II which will have another manufacturer's northbridge (from Marvell).
A more detailed overview you can find at
MorphOS-News.de, it's a report done from the official launch of the Pegasos-I at the "Amiga- & Retro-Computing-Show" in Aachen, Germany, last year. It's not up-to-date anymore, though (see above, e.g. regarding the Pegasos-II and Marvell), but should be sufficient for a first impression.
In case you've further questions or might even get interested in developing for this platform, you could contact Raquel Velasco and Bill Buck of Genesi at bbrv@genesi.lu.