Helen Hou-Sandí and Dion Hulse have been added as WordPress lead developers.
Straight from Andrew Nacin's announcement on Make WordPress Core:
The two are already highly respected leaders in the community. Dion has architected some of the most important code in WordPress over the years. He started by building the plugin updater way back in 2007, helped lay the foundations of custom post types and taxonomies, and more recently, designed and implemented automatic updates. He has essentially been one of core’s main architects for years, all while providing advice, code review to newcomers (myself included, long ago).
Helen’s tremendous impact on the project is surely known to all of you. She champions the project’s philosophies, she’s been a key leader on dozens of features large and small, including the media UI, CSS architecture, and the jam-packed WordPress 4.0 release. Her strong engineering skills are backed by her natural leadership, sound judgement for user experience design, and the mentorship of countless contributors.
It's great to see Dion and Helen as lead developers. Both certainly deserve it.
Helen works for 10up, a WordPress consulting agency, and spends nearly 100% of her time on the WordPress.org project. She received commit access in late 2012, at the beginning of the 3.6 release cycle. You can follow @helenhousandi on Twitter, and visit her website as well.
This is the first change to the list of lead developers for WordPress since Andrew Nacin became a lead in 2012, before the WordPress 3.5 release.
I asked Andrew Nacin how these decisions are made, and he responded with the following:
After each release, the lead developers review the current list of guest committers, potentially propose new committers, etc. Any proposals are finalized through consensus.
This is a big honor and an uncommon occurrence for the WordPress project. Major congratulations are due to both Helen and Dion.