I'm a bit under the weather and I'm not sure what to think of this yet. With that provision, and trying to be brief:
I agree that there are security concerns about Python 2.7 that can't be addressed by recommending Python 3.4 instead. I also agree that the ban on new features in old releases can be stifling. But I also worry about breaking working code.
I am a bit worried that writing a PEP (at least this specific PEP) would become less about arguing for a specific technical (or even political) idea, and more about putting "weasel words" in an official document so that it can be used to justify future actions without due process.