[3.9] gh-92436: __future__ docs: add note on expectations for "from __future__...

[3.9] gh-92436: __future__ docs: add note on expectations for "from __future__ import annotations" (GH-92568). (#92726)

(cherry picked from commit 6582c964)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

Doc/library/__future__.rst

@@ -90,12 +90,20 @@ language using this mechanism:
 | generator_stop   | 3.5.0b1     | 3.7          | :pep:`479`:                                 |
 |                  |             |              | *StopIteration handling inside generators*  |
 +------------------+-------------+--------------+---------------------------------------------+
-| annotations      | 3.7.0b1     | 3.10         | :pep:`563`:                                 |
+| annotations      | 3.7.0b1     | TBD [1]_     | :pep:`563`:                                 |
 |                  |             |              | *Postponed evaluation of annotations*       |
 +------------------+-------------+--------------+---------------------------------------------+
 
 .. XXX Adding a new entry?  Remember to update simple_stmts.rst, too.
 
+.. [1]
+   ``from __future__ import annotations`` was previously scheduled to
+   become mandatory in Python 3.10, but the Python Steering Council
+   twice decided to delay the change
+   (`announcement for Python 3.10 <https://mail.python.org/archives/list/python-dev@python.org/message/CLVXXPQ2T2LQ5MP2Y53VVQFCXYWQJHKZ/>`__;
+   `announcement for Python 3.11 <https://mail.python.org/archives/list/python-dev@python.org/message/VIZEBX5EYMSYIJNDBF6DMUMZOCWHARSO/>`__).
+   No final decision has been made yet. See also :pep:`563` and :pep:`649`.
+
 
 .. seealso::