Retail deliveries for the i8 started in June 2014, so presumably they had been working on a new version for two years already; unless the team was diluted to provide insight to their other teams for BMW's iPerformance effort to include technology from their i vehicles to hybrid variants of older series.
Does "launch" have a specific meaning in this context, that it's always the announcement of the final design, or the first showing at Frankfurt, or when it hits dealers?
