"the end of Geralt's saga," and not the franchise.
In fact it "will continue" beyond The Witcher 3, teased Kicinski. This echoes similar action by BioWare who are continuing Mass Effect beyond the trilogy of Commander Shephard.
Arguably this applies to Ubisoft's Assassin's Creed franchise now that main character Desmond Miles is no longer in the spotlight. It's something about the number three.
“This is the last part of the trilogy, in which there will be a great finale of the story,” Kicinski says. “However, this doesn’t mean the end of franchise. The franchise will continue.” Recently CD Projekt RED and revealed it's an entirely open world affair, apparently 20% larger than Bethesda's Skyrim.
The Witcher 3 releases on PC in 2014.