The reason Guido didn't want 3.6 to guarantee dict ordering was to protect 3.5 projects from mysteriously failing when using code that implicitly relied on 3.6 behaviors (for example, cutting and pasting a snippet from StackOverflow).

He thought that one cycle of "no ordering assumptions" would give a smoother transition. All 3.6 implementations would have dict ordering, but it was safer to not have people rely on it right away.