United Front Games announces they are not letting Sleeping Dogs lie, as they have plans for a follow on called Triad Wars, though all they are revealing right now is a 2014 release window (thanks nin via Shacknews). Here's word:

Hi everyone! We’ve been a bit tight-lipped about our current projects over here at UFG, but we’re finally able to give you a little something.

So, we’re making a new game! We can’t say a lot about it right now, but you might have read about a trademark registration for something called Triad Wars? Well, we’re super-excited that it’s another game based in the Sleeping Dogs universe, it’s something we’ve wanted to do for ages, and we’re very happy to be working with Square Enix again… but that’s all we can give you for the time being – we’ll have more information about what the game’s going to be in 2014.

As always, we love to hear your thoughts and appreciate your shared interest in the games we make – although to reiterate, we really can’t share any more details until 2014 (despite your best efforts to get them, you sneaky people!)