I found an ebuild dev-java/scala-bin-1.2.0.1 which is out-of-date. Links http://scala.epfl.ch/downloads/distrib/files/scala-1.2.0.1.tar.bz2 is dead. Also there is dev-lang/scala which is quiet up-to-date (last version is 2.10.3). But it would be good to add 2.11.0 version http://scala.epfl.ch/news/2014/04/21/release-notes-2.11.0.html
I've created an ebuild to install version 2.11.4. + 18 Jan 2015; Patrice Clement <monsieurp@gentoo.org> +scala-bin-2.11.4.ebuild: + Version bump to 2.11.4. Please try it out and reopen in case of errors. Thanks!