This is the last but one update to the 2.8 series of the Calligra Suite, and Calligra Active released to fix recently found issues. The Calligra team recommends everybody to update.
Why is 2.8.4 skipped? Shortly before 2.8.4 release we discovered bug that sneaked in 2.8.2 version and decided to skip the 2.8.4 entirely and quickly release 2.8.5 instead with a proper fix. The bug is related to not showing file formats in Save dialogs.
Also: Calligra 2.8.5 Released