Clarify indentation policy for old and new files.

pep-0007.txt

@@ -46,9 +46,13 @@ C dialect
 
 Code lay-out
 
-    - Use single-tab indents, where a tab is worth 8 spaces.
-      (For Python 3000 and entirely new source files, see the section
-      Python 3000 below.)
+    - Use single-tab indents, where a tab is worth 8 spaces, in files
+      that already use tabs.  In new source files, and the few files
+      that were created after this rule was introduced, use 4-space
+      indents and no tabs at all.
+
+      At some point, the whole codebase may be converted to use only
+      4-space indents.
 
     - No line should be longer than 79 characters.  If this and the
       previous rule together don't give you enough room to code, your
@@ -194,13 +198,6 @@ Documentation Strings
       not all do; the MSVC compiler is known to complain about this.
 
 
-Python 3000
-
-    In Python 3000 (and in the 2.x series, in new source files),
-    we'll switch to a different indentation style: 4 spaces per indent,
-    all spaces (no tabs in any file).  The rest will remain the same.
-
-
 References
 
     [1] PEP 8, Style Guide for Python Code, van Rossum, Warsaw