From the time decision is made to go into production, the time is two years. Requests for quotes have to go out to suppliers, quotes have to come in, contracts awarded, supplier ramps up, production lines set up (assuming an old plant is used and not built), employees trained, production SNAFUs ironed out. Much flurry. Used to take 5 years but they steadily whittled that down, sloughing a lot of that off to the parts suppliers. With social media these days, introduction isn't left to the last minutes before deliveries start, they try to build up the buzz rather than spring anything on their competitors because they know every one is trying to reach the same goals.