Riffing off of
@TwoSix 's thread, I would posit a setting where the magic of 5.5 fully blossoms across society, with the consequences of many high level characters and the godlike powers they possess are used to their fullest logical extent. The world would perhaps be divided into nations ruled by parties of epic adventurers struggling with each other while simultaneously crushing the last pockets of "monster" resistance. Formal schools teaching different kinds of magic and PC class skills would exist, and the world would in many ways resemble the modern one I think.
Really break that medieval stasis, as
@DEFCON 1 would say.