GitHub has fine grained access permissions. We currently have a Community Team, which anyone is welcome to join, and can be notified on GitHub by mentioning @InsightSoftwareConsortium/community. This group currently has limited rights. There are currently also repository-level teams. As we transition, we will likely refine the teams.
The release schedule has been updated on the wiki.
The release process will start on April 13th with the call for patches, and will finish on May 18th with the actual official release. Since this release is going to include a lot more changes than the previous ones, we foresee more (unexpected) problems and therefore extended the release schedule compared to the previous release.