As of today, IDF v5.0 has entered the 18 month Maintenance period which is defined by Espressif as:
During the Maintenance period, the version is still supported but only bugfixes for high severity issues or security issues will be applied.
v5.1 is recommended for new designs and, if you haven’t already, you should begin planning to migrate your firmware off older versions.
As of this writing, v5.1.2 is the latest stable release.
As a reminder, here is the current IDF maintenance and end-of-life roadmap.