The most obvious design cues from the i8 Spyder concept are the targa-style roof and the cowls behind the seats. There are some minor tweaks, of course. The cowls aren't as flat or broad as on the concept, and they dip down to the height of the engine cover quite quickly. Though not as dramatic as the concept's, the production car's design should provide much better rearward vision. Despite that, the taillight winglets from the production coupe and the concept have been preserved, and they still flow into the cowls. The concept used a two-section folding roof for its convertible action, and that's expected to make it through to production.
Otherwise, the rest of the car is standard i8 fare, just without a top. When we last heard about the i8 Spyder, it was confirmed for production in 2018. Considering how little false bodywork is on this car, we'd say development must be pretty close to finishing up, and the car should hit the 2018 date with no issues. The i8 coupe is expected to get a power bump to about 420 hp next year, and the Spyder version should use that same updated hybrid powertrain.