If the rumors turn out to be true and Toyota does decide to go ahead and build a production variant of the roadster, then it will most likely be equipped with the same powertrains as the iQ hatchback, including the 1.0-liter and 1.33-liter gasoline engines and quite possibly, a 1.4-liter diesel. However, since we have a long way to go before the 41st Tokyo Salon opens its doors to the public, we're keeping this on Rumorville for now.
Source: Motor Magazine