Update release files to start next release

CHANGES.html

@@ -50,6 +50,21 @@ the cracks, unfortunately.  If you, as a user, can suggest improvements
 to this file based on your experience, please contribute a patch or drop
 us a note on ns-developers mailing list.</p>
 
+<hr>
+<h1>Changes from ns-3.28 to ns-3-dev</h1>
+<h2>New API:</h2>
+<ul>
+</ul>
+<h2>Changes to existing API:</h2>
+<ul>
+</ul>
+<h2>Changes to build system:</h2>
+<ul>
+</ul>
+<h2>Changed behavior:</h2>
+<ul>
+</ul>
+
 <hr>
 <h1>Changes from ns-3.27 to ns-3.28</h1>
 <h2>New API:</h2>

RELEASE_NOTES

@@ -9,6 +9,31 @@ http://www.nsnam.org including tutorials: http://www.nsnam.org/tutorials.html
 Consult the file CHANGES.html for more detailed information about changed
 API and behavior across ns-3 releases.
 
+Release 3-dev
+=============
+
+Availability
+------------
+This release is not yet available.
+
+Supported platforms
+-------------------
+This release is intended to work on systems with the following minimal
+requirements (Note:  not all features available on all platforms):
+
+This release has been tested on the following platforms:
+
+New user-visible features
+-------------------------
+
+Bugs fixed
+----------
+
+Known issues
+------------
+In general, known issues are tracked on the project tracker available
+at http://www.nsnam.org/bugzilla/
+
 Release 3.28
 ============