I have been informed by Snow that the RetroAchievements devs are going to begin the dev rollout for Dolphin on Feb 1

Rollout will be for developers only, with some people given permissions to do player testing. Rollout will be indefinite with no end date until we're satisfied with the player testing, and we expect somewhere around three months.

At that point RC will coordinate with Dolphin about properly announcing and releasing achievement functionality to all players.