Is this coming out in 2010? If so, ME2 can go to hell with the Drakensang prequel also coming out.
If those 'assassins of kings' are the Nilfgaardian agents they appear to be, sent to assassinate all the Kings of the Northlands in preparation
of a new invasion (Witcher takes place a couple of years after the Battle fo Brenna), the story could be quite interesting.
In addition, hopefully the whole "Personal History" questline of the first game will be continued... and Geralt's miraculous return to the land of the living will be explained.