Released on 7th December 2010. The ChangeLog is big: http://freeciv.wikia.com/wiki/NEWS-2.2.4 Just renaming the ebuild works fine for me.
Created attachment 257874 [details, diff] diff -u freeciv-2.2.3.ebuild freeciv-2.2.4.ebuild for QA reasons: - remove sys-libs/readline, sys-libs/zlib and app-arch/bzip2 from DEPEND and RDEPEND, as they are all three part of the base system set.
2.2.4 is in portage.