Gnome 3 will arrive a little late for Gentoo/Sabayon, here is a topic about Gnome3:viewtopic.php?f=3&t=23529
You could install it using portage, with the Gnome overlay, but if you have not good experience using portage, I don't recommend doing it, it could result in a bad experience for you
If you plan to use portage as your main package manager, you could consider doing it.
Here is why it using alien
And here is a translation of this Italian post:viewtopic.php?f=24&t=23552#p132196
Installing software from sources other than your package manager is often a bad idea (in contrast to many internet guides and tutorials for Debian/Ubuntu). There are many, many reasons that makes this choice very unsuitable, not only in the Sabayon or Gentoo world, but in any Linux distro. The most relevant and immediate ones are:
* If you install a package using make && make install
or any other package manager, your main package manager does not know that you installed that package and can't match its files with the package, meaning that most likely it could overwrite or misconfigure your system in the near future, it can't even, obviously, let you manage that package or check its dependencies.
* If you install a package converting it from <any package format> -> Sabayon/Gentoo package format you have no clue if the package conversion was successful and if it works nicely, there could be inconsistencies or subtle incompatibilities that could make your system (and the application) unstable.
You should not do such things.
If it is really unavoidable, I seen rpm
on portage, I even used them in the past on a Gentoo installation, but all of the points above are still valid, if you use them, entropy and portage have no idea of what you did.
In all this time using Sabayon it never happened to me not to find an application that I was looking for neither in entropy nor in portage. Even if it happens, you can always request for its addition in the entropy repository:viewtopic.php?f=76&t=13891