Your 2019 idea probably only works if PS5 comes out. Otherwise you have XB1 owners wanting games, developers making games for PS4 and PC still, yet XB1 owners not getting games and having to buy a new console. That's very irregular. Normally a platform is maintained somewhat until devs naturally move on. Stopping devs from making games for a platform and losing out on that money and pissing off your owners seems a Bad Idea.