Maybe I'm crazy, but whistling to get guards' attention doesn't seem too stealthy. Styx: Master of Shadows, from developer Cyanide Studio, is slated for a PC release. You'll play as the titular Styx, an ancient goblin infiltrating a miles-high tower guarded by humans, elves, and monstrous scientific experiments.
As an ancient goblin who is a master of stealth and murder, I'm not sure how the RPG elements -- gaining new abilities are you progress up the tower -- make any sense. I guess you never stop learning.
Still, a new stealth game, and one where you play as an ugly goblin. I'm interested.