Automakers and auto dealers better enjoy the good times while they last because new car sales are going to begin sliding after this year, with a serious drop off by 2017, according to a new study. AlixPartners, a global business advisory firm, suggests automakers will sell 12 million vehicles a year in the near future. The industry is tracking for a 16-million to 16.5-million unit sales year right now, but they predict that’s all going to come to an end.