I'm sure this is related to the healing of the fork with io.js via forming a new foundation. After the merge, there won't be any desire for a single person who

I'm sure this is related to the healing of the fork with io.js via forming a new foundation. After the merge, there won't be any desire for a single person who is "the node.js maintainer" anymore (because the new governance model shares responsibility), so it makes sense that the current one will step down.