This bug tracks the implementation of EAPI 3 in portage.
Decision in the 2009-12-07 council meeting:
"Because prefix support will be EAPI-3 (see below), the EAPI items referenced here will be referred to as EAPI-4 in the future."
This is fixed in 188.8.131.52.
Re-opening, pending resolution of bug 211529, bug 322049, and anything more that may arise.