update whatsnew

doc/source/whatsnew/v0.24.1.rst

@@ -30,14 +30,20 @@ The default *behavior*, however, remains the same: the result is sorted, unless
 2. ``self`` or ``other`` is empty
 3. ``self`` or ``other`` contain values that can not be compared (a ``RuntimeWarning`` is raised).
 
-This change will allow to preserve ``sort=True`` to mean "always sort" in a future release.
+This change will allow ``sort=True`` to mean "always sort" in a future release.
 
 The same change applies to :meth:`Index.difference` and :meth:`Index.symmetric_difference`, which
 would do not sort the result when the values could not be compared.
 
-For :meth:`Index.intersection` the option of ``sort=True`` is also renamed
-to ``sort=None`` (but for :meth:`Index.intersection` it is not the default), as
-the result is not sorted when ``self`` and ``other`` were identical.
+The `sort` option for :meth:`Index.intersection` has changed in three ways.
+
+1. The default has changed from ``True`` to ``False``, to restore the
+   pandas 0.23.4 and earlier behavior of not sorting by default.
+2. The behavior of ``sort=True`` can now be obtained with ``sort=None``.
+   This will sort the result only if the values in ``self`` and ``other``
+   are not identical.
+3. The value ``sort=True`` is no longer allowed. A future version of pandas
+   will properly support ``sort=True`` meaning "always sort".
 
 .. _whatsnew_0241.regressions: