I didn't see any open bugs nor ebuild in portage for dev-ruby/rails-4.0.1 which was released Nov 1st. http://weblog.rubyonrails.org/2013/11/1/Rails-4-0-1-has-been-released/
We are aware of the new version via http://moving-innovations.com/~graaff/outdated-gems/ I have the ebuilds mostly ready, but I also want to mark them ready for ruby20 at the same time and this is not finished yet.
Rails 4.0.2 is now available in the tree (expedited due to security issues, so sadly still without ruby20 support).