sci-libs/blas-atlas, etc., use the latest stable version of Atlas, 3.6.0. There have been a number of updates to that; I just downloaded and compiled 3.7.10 from Sourceforge. There are a number of improvements, especially in support for 64-bit processors, plus some bugfixes, in 3.7.10. I'm not sure how rapidly it is changing, though -- they went from 3.7.8 to 3.7.10 in a couple of weeks. I'd like to have 3.7.10 ebuilds available, even if they have to be package masked.
It appears these packages are now in portage but this bug was not closed. Thanks for reporting - closing this bug as they are now in the testing branch.