There is a sequel to the game, for mobiles; xiii: covert identity

That is true. Released by Gameloft back in 2007. Played it on my Nokia N8 but it never really captured that feel like Ubisoft's XIII did. Many people are waiting for a proper 3D sequel but this is still a rock solid game :). Cheers

Well if the remake does well, maybe we'll get a proper 3D sequel.

Also, does Covert Identity resolve the cliffhanger?

I hope it does well this time. Ubisoft did a poor job promoting the game back then. As for Covert Identity, i honestly can’t remember as i played it a long time ago. I think that it also did not completely finish the story as there are 18 comics in the XIII franchise as far as i know. It did continue the story after Ubisoft’s XIII but i was not really paying much attention to the story. We are talking about a 2D java game played on a Nokia more than 10 years ago ;). Cheers