Games, especially massive open world fantasy games, take a long time to develop nowadays. Witcher 2 came out 2011, and the new one came out in 2015, that's 4 years right there. If you look at other developers who create some what similar games you'll find a turn around of 4-5 years.
This is speculation on my part, but I could see them delaying it because they want the release to coincide with the release of their new system, so they'll release it on the wii u and possibly whatever new console or handheld they have.







