The next anticipated release after Isabelle2025 (March 2025) will be Isabelle2025-1 (December 2025). The hot phase of the release is presently scheduled for 03-Nov-2025..15-Dec-2025. The detailed plan is as follows:

• 06-Oct-2025: Isabelle2025-1-RC0 as informal preview
• 03-Nov-2025 Isabelle2025-1-RC1 as first formal release candidate
• 15-Dec-2025: final and unchangeable Isabelle2025-1 release

Important: Contributors need to have things ready for RC1 or RC2. There need to be several weeks left to consolidate everything, before the release becomes final and unchangable (until the subsequent release).