Rewrite the deprecation/removal timeline

Author: emmatyping

peps/pep-0784.rst

@@ -197,25 +197,35 @@ Other compression modules
 New import names ``compression.lzma``, ``compression.bz2``, and
 ``compression.zlib`` will be introduced in Python 3.14 re-exporting the
 contents of the existing ``lzma``, ``bz2``, and ``zlib`` modules respectively.
-Starting with Python 3.19, the existing modules will emit a deprecation warning
-on import. In Python 3.24, the existing modules will be removed and code must
-use the ``compression`` sub-modules. The documentation for these modules will be
-updated to discuss the planned deprecation and removal.
 
 The ``_compression`` module, given that it is marked private, will be
 immediately renamed to ``compression._common.streams``. The new name was
 selected due to the current contents of the module being I/O related helpers
 for stream APIs (e.g. ``LZMAFile``) in standard library compression modules.
 
+Compression module migration timeline
+-------------------------------------
+
+Existing modules will emit a ``DeprecationWarning`` in the Python
+release following the last Python without the ``compression`` module leaving
+support. For example, if the ``compression`` namespace is introduced in 3.14,
+then the ``DeprecationWarnings`` would be emitted in 3.19, the next release
+after 3.13 reaches end of life. Following the standard deprecation timeline
+specified in :pep:`387`, in Python 3.24 the existing modules will be removed
+and code must use the ``compression`` sub-modules. The documentation for these
+modules will be updated to discuss the planned deprecation and removal
+timelines.
+
+
 Backwards Compatibility
 =======================
 
 The main compatibility concern is usage of existing standard library
 compression APIs with the existing import names. These names will be
-deprecated, and will be removed in 3.24. Given the long deprecation period,
-most users will likely migrate to the new import names well before then.
-Additionally, a libCST codemod can be provided to automatically rewrite
-imports, easing the migration.
+deprecated in 3.19 and will be removed in 3.24. Given the long coexistance of
+the modules and a 5 year deprecation period, most users will likely migrate to
+the new import names well before then. Additionally, a libCST codemod can be
+provided to automatically rewrite imports, easing the migration.
 
 Security Implications
 =====================