We need to start thinking of the coming Isabelle2018.
Counting 10 months forwards from Isabelle2017, it should be published in
the first half of Aug-2018.
Counting 6 weeks backwards and taking FLoC/ITP into account,
Isabelle2018-RC1 should appear shortly before 01-Jul-2018.
I will probably make Isabelle2018-RC0 as informal test in June, although
interested people can test
https://isabelle.sketis.net/devel/release_snapshot every day. (There are
still many Windows/Cygwin components that don't work, due to the change
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