Upstream just released geary 0.8.0. Simple rename of existing ebuild works fine - there arent many new changes in this release (mostly bugfix and composer ui).
+*geary-0.8.0 (20 Sep 2014) + + 20 Sep 2014; Julian Ospald <hasufell@gentoo.org> +geary-0.8.0.ebuild: + version bump wrt #523286