The next anticipated release is Isabelle2021-1 (December 2021): as the distance between two releases is usually 8–10 months, there are sometimes 2 releases per year. This explains the slightly odd name tag, but in all other respects, Isabelle-2021-1 should be a perfectly normal official release.

The hot phase with release candidates will be 01-Nov-2021 .. 15-Dec-2021.