There's currently 72 fixes in freeciv-3.1 branch (S3_1) since 3.1.5 release.
There's currently no blocking issues preventing 3.1.6 release: https://redmine.freeciv.org/issues/1696
3.1.6 is expected to be the last release from the freeciv-3.1 series.
Towards 3.1.6
Re: Towards 3.1.6
As freeciv-3.1 reach End-of-Life with 3.1.6 release, also its nightly builds directory https://files.freeciv.org/nightly/S3_1/ will be removed after the release. That directory has some assets that are not published for official releases, such as the full set of the appimages. Be sure to save to yourself any you want to keep, before they get deleted.