Good luck convincing some here of this...I'm not arguing entirely against change. Continuity can and should progress. The world should grow and shift and alter naturally. Characters die or retire, kings are overthrown, villains are defeated, etc. That's all good. But that doesn't change canon, that adds to canon.

The various major upheavals and "game-changing" developments along the timelines/editions of the Forgotten Realms, such as the Spellplague to name just one contentions example, would fit into your definition as well. But to many, some of them were the worst thing ever to happen to their beloved setting. So, as a few here have continued to press upon: "good" changes are "canon enhancing", "bad" changes are "cannon destroying." And *that* is subjective.