If you did not migrate your account yet, visit https://idp-portal-info.suse.com/
Leap 15.4 is under development. For details check the packaging information and the Roadmap. openSUSE Leap 15.4 offers professional users, entrepreneurs and ISVs (Independent Software Vendors) updated support for modern hardware with improved YaST functionality and an improved installer. Leap 15.3 was released to the general public on June 02, 2021.
Leap 15.4 is based on the Portal:Jump concept, where we combine openSUSE Backports with binaries from SUSE Linux Enterprise.