Ubisoft CEO, Yves Guillemot, said during an interview at Gamescom 2013 that the digital-only copy of Far Cry 3: Blood Dragon had sold over 1 million copies so far. Considering Blood Dragon was very much an experiment of a game, this is a great step for the company.
Blood Dragon took a chance by using the theme of an action movie set in the 80s, which took place in a futuristic island that had enemies like the Cyber Shark and the Metal Mantaray. Blood Dragon never took itself seriously, but gamers on the other hand, took it seriously with their wallets. Guillemot said that the digital-only format allowed a lower profit point, which allowed them to stretch out the experiment.
Obviously with less risk involved, the bigger the chance they can take. The Ubisoft CEO hinted that Blood Dragon might make it to a full retail release, which would see sales jump even more so.