I'm dubious of this multi marriage bit coming to the sims. I don't want it and I have no interest in it. I prefer all my sims, the ones in my rotation at the very least, to be monogamous. That sort of flies against the relationship type I'm after. There is already one mod, everybody knows it's name, that offers players a chance to do that, or equally bad romantic/sexual things. I can't imagine the Gurus wanting to bring that into the game. That pushes boundaries way too far and is too risky from both a ratings and sales standpoint. EA and Maxis aren't going to risk the bottom line for something that far out on the fringe. Unless they've lost their minds.
I haven't heard of this tweet until now, but it feels like a joke gone awry, or simply in very bad taste.