Dont you think it's time to tag development-sources-2.6.4.ebuild as stable? Users on "x86" still get 2.6.4rc1 -- a kernel that has problems for example with usblp. Is there any reason, why an official stable *released* kernel is tagged as unstable in gentoo? Why should x86-users stay with a release-candidate that contains bugs?
We just had to update the ebuilds to contain correct information about kernel configuration (see bug #45559). It's done now and 2.6.4 is marked as stable on x86.