Whatever updates were made to this version aren't visual (except for the paint), as the one Chris Harris drove last spring and another seen hot-weather testing in Nevada both had production bodies. We presume the changes are relatively minor and more than skin deep – perhaps brake calibration, suspension tuning or tweaks to the powertrain – but Porsche didn't release any more information.
The 918 Spyder is Porsche's latest supercar, which will compete with the LaFerrari and the McLaren P1 hybrid supercars. The Porsche may be the underdog of the group when considering horsepower, acceleration, top speed and price, but the 887-horsepower brute has the most advanced hybrid drivetrain of the three.
UPDATE: Porsche corrected its earlier tweet, saying, "The earlier image of the 918 Spyder is the latest pre-production version. The production version will be unveiled at Frankfurt."