This is not at all an apt comparison. With Django, you're buying into its templating, routing system, its ORM, its view/controller paradigm, its central app configuration, its core request delivery system, whatever it does for caching/sessions, and all the admin stuff. With Pylons, you've bought into some choice of templating (usually Mako), routing system (Routes), some choice of ORM (usually SQLAlchemy), its view/controller paradigm, its central app configuration, its core request delivery system (Paste, PasteScript, etc.), caching/sessions (Beaker), and it doesn't come with any admin stuff.

Pylons' change to Pyramid most certainly does not replace that whole stack. It replaces exactly two of those components, the view/controller paradigm and central app configuration. All the things that don't change at all are: templating, ORM, routing, Paste/Pastescript, caching/sessions still on Beaker.

So this nothing at all like moving to an entirely new framework, Mako/SQLAlchemy/Beaker aren't going anywhere.

edit: the routing changes a bit, but its an improved and higher performing package with mostly complete feature parity. I'm looking forward to using it.