Filing this bug as #472850 is for =dev-java/maven-bin-3.1.0. Maven 3.1.1 is required for some plugins to properly function, e.g. android-maven-plugin, so some people have to wait for a bump or install into ~/local :D I can provide some help if there's additional issue around the version bump.
+ 11 Nov 2013; Tom Wijsman <TomWij@gentoo.org> +maven-bin-3.1.1.ebuild: + Version bump to 3.1.1, unbundled more dependencies.
Added mention of this bug report to the ChangeLog. Thank you very much for reporting the version bump.