dev-db/mysql version 5.6.11 is available at http://dev.mysql.com/downloads/mysql/ Since version 5.6.10 MySQL 5.6 series has reached "General Availability" status.
We have mysql-5.6.10 and mysql-5.6.12 in the mysql overlay[1] [1] - http://git.overlays.gentoo.org/gitweb/?p=proj/mysql.git;a=summary