We play the Titans on May 3 (Sat), the Centenary Test is on May 9 (the Friday after) so going off what they have done in the past, the Kangaroos players will be not playing in the round we play the Titans.
I wouldn't be getting too excited about Prince not playing against us yet, Lockyer might still play for Australia, given he is expected to play against the Bunnies this weekend. In that case they will probably go with Thurston and Lockyer. Even if Lockyer is out, I wouldn't be surprised if they picked Cronk as he is the incumbent.
So in other words, we are just about gauranteed to be missing Gidley, and the Titans have some chance of missing Prince