Please bump dev-libs/libwacom to 0.12. Renaming the ebuild is enough.
+*libwacom-0.12 (27 Mar 2015) + + 27 Mar 2015; Alexandre Rostovtsev <tetromino@gentoo.org> + -libwacom-0.10.ebuild, +libwacom-0.12.ebuild: + Version bump (bug #544616, thanks to Chí-Thanh Christopher Nguyễn), adds + support for cintiq 27qhd, dtu-1031x, pen medium; improves udev rules to avoid + misidentifying as a joystick/touchpad.