We are heading towards the Isabelle2018 release, which is scheduled for August 2018. This spot provides a reference for upcoming release candidates.
Isabelle2018-RC0 (06-Jun-2018): informal snapshot for experimentation. See also AFP/7f9c8aca53e8.
Isabelle2018-RC1 (02-Jul-2018): first official release candidate; almost everything ready, but some documentation still needs update. See also AFP/2af750da996c.
Update of Poly/ML component: slightly improved performance and more robust.
Update of Kodkodi component for Nitpick on Windows (back to status-quo from Isabelle2017).
Session HOL-Real_Asymp by Manuel Eberl.
Further library tuning of HOL, HOL-Analysis, HOL-Algebra.
Update of Poly/ML component: proper monitoring of ML threads.
Update to latest Java 8 release: jdk-8u181.
More command-line options for isabelle vscode_server (relevant for VSCode settings isabelle.args).
Isabelle Server: allow to specify timeout for use_theories.
Proper treatment of forked proof within context of subgoal premises.
More robust build of HOL-Proofs with threads=2.
More flexible document build script.
Clarified word characters in Isabelle/jEdit to accommodate \<^control> symbols.
Fine-tuning of isabelle build options -c -x -B.
Fine-tuning of Isar command span range: relevant for checking of formal comments.
Removed Sledgehammer prover veriT: not ready for release.
The Isabelle release process is subject to the laws of causality: release candidates can be modified, but the final release is unchangeable. This means that testing needs to happen in the weeks before the final release.
The main forum for discussion of Isabelle2018 release candidates is on isabelle-users mailing list.
Update 15-Aug-2018: The final release of Isabelle2018 (August 2018) is available from the Isabelle website. The above release candidates will disappear eventually.