It'll be interesting to see if/how the Y affects 3 sales ... but there's another aspect of the Y that could mean a difference in the 3 itself: hardware innovations. Musk has touted the Y's reduction in wiring and changes to the frame to make them simpler to produce. I have to think those innovations will be transferred to the 3 production line as well. Less wiring == more reliability and simpler production == lower cost/higher profit.