EAPI 5 includes support for automatic rebuilds via the slot-operator and sub-slots, which has potential to make @preserved-rebuild unnecessary (see Diego’s blog post regarding symbol collisions and bug #364425 for some examples of @preserved-rebuild shortcomings). Since this support for automatic rebuilds has potential to greatly improve the user-friendliness of preserve-libs, I have decided to make preserve-libs available in the 2.1 branch of portage (beginning with portage-2.1.11.20). It’s not enabled by default, so you’ll have to set FEATURES=”preserve-libs” in make.conf if you want to enable it. After EAPI 5 and automatic rebuilds have gained widespread adoption, I might consider enabling preserve-libs by default.