Minor version updates of 9.x series are progressing as decided and Drupal 9.4.0 got released, yesterday. Gábor Hojtsy, Drupal Initiative Coordinator working at Acquia posted about it in drupal.org.
The fourth feature release of Drupal 9 brings a whole new frontend look with the Olivero theme by default and a refreshed backend interface with the Claro theme. Claro had became default backend theme from the major version release of Drupal 9.0.0 itself and is now stable. There is also a new starterkit theme generator, better image loading performance and easier permission management.
Olivero is named after Rachel Olivero (1982-2019). She was the head of the organizational technology group at the National Federation of the Blind, a well-known accessibility expert, and a Drupal community contributor. Olivero theme is WCAG AA complaint. It means, the theme follows the guidelines related to the accessibility of web content.
Since minor releases are backwards-compatible, modules, themes, and translations that supported Drupal 9.3.x and earlier will be compatible with 9.4.x as well. However, the new version does include some changes to strings, user interfaces, internal APIs, and API deprecations. This means that some small updates may be required for your translations, modules, and themes. Read the 9.4.0 release notes for a full list of changes that may affect your modules and themes.