From what I understand the 4.0.0 release was to merge NodeJS and io.js into one stable product as soon as possible. 5.0.0 now goes further in integrating featur

From what I understand the 4.0.0 release was to merge NodeJS and io.js into one stable product as soon as possible. 5.0.0 now goes further in integrating features that were not ready to release at that time. Further major version updates are to be less frequent.