Well, maybe not a total abdication, but Jimbo has relinquished a substantial portions of his powers. See his announcement and the context.
In an upcoming academic article I discuss why calling Wikipedia a monarchy/dictatorship, while not too off the mark in its very early stages, is no longer true. It's nice not to be contradicted by the current events :)
News on Wikipedia: Leicester City win historic Premier League title - Once rank outsiders, association football club Leicester City won the Premier League this week to cap a memorable season in England's top division.
10 hours ago