Model years are very much alive and well. It was easy when you made 3-4 models to have switch over at about the same time so they could all launch June-August, but when you have 8, 9, 10 or more models there is such a manpower and resource squeeze that you have to stagger them a bit more. Also it tends to be just first or last year versions of a model that have a particularly long or short model year.
BTW, it's a purely North American concept. For the rest of the world a 2014 model year is a vehicle that is built between Jan 1st and Dec 31st of 2014. If you change from gen I to gen II of the same vehicle in that time they are still both 2014 cars. So you can and do have for example both a 1998 E36 and a 1998 E46 3 series in Europe. That can make it hard for tracking running changes on European cars.
