The way it is now, kde-4.0.0 depends on, for example: kde-base/kdelibs:kde-4 namely, the dependency is on the slot, instead of the exact version. Therefore, if there is a previous version with the same slot, like on of the release candidates, kde-4.0.0 won't update them to version 4.0.0. Likewise, when kde-4.0.1 will be out, emerging kde-4.0.0 will not downgrade to 4.0.0 version from 4.0.1. Reproducible: Always Steps to Reproduce: 1. 2. 3.
Sounds like a feature to me.
Fixed in CVS, thanks for the bugreport.