I am announcing here the release of the ebuilds collection of mate-desktop for gentoo. All ebuilds support building with traditional GTK+2 and the newer GTK+3.
You should be able to use those ebuild with layman adding my overlay found at the following repository oz123/mate-de-gentoo.
In the mean while some packages have been already updated to 1.14.1 by mate developers. These will come soon into the overlay.