Physic: I'm not sure that's the case, based on experience with XI. It never had any drastic complete reworkings of the battle system, but there will still things at multiple points in the game that changed almost everything about how battles played out and changed the character of the game almost as drastically. However, your point that 1.20 is the mechanical underpinning of the future battle system is valid - which is why I'm holding my own criticism of enmity and class balance until 1.20 hits.