At first, it's not immediately evident that this is the Spyder version. However, upon closer inspection of the top of the car, it's clear that this isn't a standard i8.
Video description (via YouTube/Supercarsfromeu):
"This video features a BMW i8 SPYDER spied testing on the Nurburgring."
Some specs, background info, etc.
The current i8 coupe is powered by a turbocharged 1.5-liter 3-cylinder producing 362 horsepower, which is able to reach 0-62 mph in 4.4 seconds with a top speed of 250 km/h (155 mph). i8 Spyder is rumored to feature similar specs. The codename given for the new convertible is I15.
The exact release date for the i8 Spyder has not yet been revealed. However, Harald Krüger, Chairman of the Board of Management of BMW AG, confirmed that the BMW i8 Spyder will arrive sometime in 2018.
Top Still Looks A Bit Rough (via YouTube/Supercarsfromeu)