1.3.1 had couple of nasty bugs, like infinite recursion in some cases etc. I'd be nice to have 1.4.0 asap
Renaming the 1.3.1 ebuild and upgrading to a recent version of six (dev-python/six-1.6.1) seems to be ok for my usual work. While using dev-python/six-1.3.0 I got some dependency errors.
*matplotlib-1.4.0 (14 Sep 2014) + + 14 Sep 2014; Justin Lecher <jlec@gentoo.org> +matplotlib-1.4.0.ebuild: + Version Bump, #521830 +