Bring PEP 453 What's New entry up to date

We changed a few details of the pip integration over the course
of the Python 3.4 beta and release candidate cycle, but I hadn't
updated the What's New entry appropriately.

The Py2/Py3 split on POSIX and the generally challenges of
dealing with parallel installs means we haven't attained
complete consistency across all environments, but hopefully
this updated text is clearer about the end result.

Relevant to issue #20909.

Doc/whatsnew/3.4.rst

@@ -187,16 +187,23 @@ Bootstrapping pip By Default
 
 The new :mod:`ensurepip` module (defined in :pep:`453`) provides a standard
 cross-platform mechanism to bootstrap the pip installer into Python
-installations and virtual environments.
-
-By default, the scripts ``pipX`` and ``pipX.Y`` will be installed (where
-X.Y stands for the version of the Python installation), along with the
-``pip`` Python package and its dependencies.
+installations and virtual environments. The version of ``pip`` included
+with Python 3.4.0 is ``pip`` 1.5.4, and future 3.4.x maintenance releases
+will update the bundled version to the latest version of ``pip`` that is
+available at the time of creating the release candidate.
+
+By default, the commands ``pipX`` and ``pipX.Y`` will be installed on all
+platforms (where X.Y stands for the version of the Python installation),
+along with the ``pip`` Python package and its dependencies. On Windows and
+in virtual environments on all platforms, the unversioned ``pip`` command
+will also be installed. On other platforms, the system wide unversioned
+``pip`` command typically refers to the separately installed Python 2
+version.
 
 The :ref:`pyvenv <scripts-pyvenv>` command line utility and the :mod:`venv`
 module make use of the :mod:`ensurepip` module to make ``pip`` readily
-available in virtual environments. When using the command line utility, ``pip``
-is installed by default, while when using the :mod:`venv` module
+available in virtual environments. When using the command line utility,
+``pip`` is installed by default, while when using the :mod:`venv` module
 :ref:`venv-api` installation of ``pip`` must be requested explicitly.
 
 For CPython :ref:`source builds on POSIX systems <building-python-on-unix>`,
@@ -204,15 +211,31 @@ the ``make install`` and ``make altinstall`` commands bootstrap ``pip`` by
 default.  This behaviour can be controlled through configure options, and
 overridden through Makefile options.
 
-On Windows and Mac OS X, the CPython installers now offer the option to
-install ``pip`` along with CPython itself.
+On Windows and Mac OS X, the CPython installers now default to installing
+``pip`` along with CPython itself (users may opt out of installing it
+during the installation process). Window users will need to opt in to the
+automatic ``PATH`` modifications to have ``pip`` available from the command
+line by default, otherwise it can still be accessed through the Python
+launcher for Windows as ``py -m pip``.
 
 As `discussed in the PEP`__, platform packagers may choose not to install
-``pip`` by default, as long as the command ``pip``, when invoked, provides
-clear and simple directions on how to install ``pip`` on the platform.
+these commands by default, as long as, when invoked, they provide clear and
+simple directions on how to install them on that platform (usually using
+the system package manager).
 
 __ http://www.python.org/dev/peps/pep-0453/#recommendations-for-downstream-distributors
 
+.. note::
+
+   To avoid conflicts between parallel Python 2 and Python 3 installations,
+   only the versioned ``pip3`` and ``pip3.4`` commands are bootstrapped by
+   default when ``ensurepip`` is invoked directly - the ``--default-pip``
+   option is needed to also request the unversioned ``pip`` command.
+   ``pyvenv`` and the Windows installer ensure that the unqualified ``pip``
+   command is made available in those environments, and ``pip`` can always be
+   invoked via the ``-m`` switch rather than directly to avoid ambiguity on
+   systems with multiple Python installations.
+
 
 Documentation Changes
 ~~~~~~~~~~~~~~~~~~~~~
@@ -229,16 +252,6 @@ However, as this migration is currently still incomplete, the legacy
 versions of those guides remaining available as :ref:`install-index`
 and :ref:`distutils-index`.
 
-.. note::
-
-   To avoid conflicts between parallel Python 2 and Python 3 installations,
-   only the versioned ``pip3`` and ``pip3.4`` commands are bootstrapped by
-   default when ``ensurepip`` is invoked directly (including by the CPython
-   installers). ``pyvenv`` ensures that the unqualified ``pip`` command is
-   made available in virtual environments, and ``pip`` can always be
-   invoked via the ``-m`` switch rather than directly to avoid ambiguity on
-   systems with multiple Python installations.
-
 .. seealso::
 
    :pep:`453` -- Explicit bootstrapping of pip in Python installations