MATE 1.14 has been released on April 8th. Please bump. The ebuilds from inofficial rinaldus-overlay work fine for me.
Gentoo devs are aware of 1.14 release: https://bugs.gentoo.org/show_bug.cgi?id=567702#c9 As the comment says please be patient. *** This bug has been marked as a duplicate of bug 567702 ***