[Python-Dev] Status regarding Old vs. Advanced String Formating

Hi, I was of the thought that Old String Formatting |"%s" % foo| was to be phased out by Advanced String Formatting |"{}.format(foo)|. I however keep seeing new code committed into the main VCS using the old style. Is this okay? Is there a policy? I ask also because I expect CPython to lead by example. On another note, will the old format ever be deprecated? Is there a date?