According to creative director Jonathan Morin, the "average player" who "does free roam a bit" will reach the end of Watch Dogs within 35-40 hours. Completing 100 per cent of the game, meanwhile, will take you closer to 100 hours.
Morin later elaborated on this on Twitter, noting that the game features a combination of endless and non-endless events, the latter of which can be "completed" while the former can potentially go on forever. Specifically, the "Potential Crimes" aspect of the game is constantly randomly generated in a similar fashion to the Radiant quest system in Skyrim, and online play will always be available, too.
Ubisoft also confirmed that the game's delay was not only to polish up the existing content, but also to add some new material, too. The content in question has caused its age rating from the Australian Classification Board to be upgraded from MA15+ to R18+ due to newly added references to sexual violence. This is not permitted under an MA15+ rating, and so the new content for the game had to be resubmitted to the ACB.
The scene in question reportedly revolves around human trafficking and the implied sexual abuse of a 19-year old female Romanian immigrant. According to the ACB report, the room into which the young girl is pulled is set up with video cameras and filming equipment, and as the male character in the scene moves away from the bed, "several blood spots are visible on the bed sheets."
Speaking with Kotaku Australia, Ubisoft confirmed the new content.
"The entire development team has been working hard to polish and fine-tune Watch Dogs in order to deliver a truly memorable open-world game," read the statement. "In parallel, the extra time also allowed the team to include a bit of additional content."
Australia's R18+ classification is a relatively new addition to its game rating systems; prior to January of last year, the newly expanded version of Watch Dogs would have been refused classification in Australia and would have had to be censored in order to be released. An ESRB classification for the US release of the game does not appear to have been recorded as yet.