If traders buy alts with btc, btc drops and alts go up, could happen for wathever reason. My theory is that btc will drop, and that traders will go to fiat AND alts, then, after some news, people will buy btc again, and also alts, what will make all the cryptosphere go up. Or maybe alts will just consolidate while btc drop before going up again or all will drop or maybe rally ... Nobody really knows ...