Python Language Moratorium
Brett Cannon, Jesse Noller, Guido van Rossum · Apress eBooks · 2010
This PEP proposes a temporary moratorium (suspension) of all changes to the Python language syntax, semantics, and built-ins for a period of at least two years from the release of Python 3.1. In particular, the moratorium would include Python 3.2 (to be released 18–24 months after 3.1) but allow Python 3.3 (assuming it is not released prematurely) to once again include language changes.