I think it's pretty obvious we'll be seeing some form of Communism/Socialism in the game. One might argue that the Big Sister already does - she's kidnapping the little girls for the 'good of the whole' in Rapture (the splicers and giving the Big Daddies things to do) and putting herself in charge of watching over these groups. She uses force ('big government') to put down the renegade individual, the prototype Big Daddy, from disrupting things for the good of everyone else. These messages are simply being done somewhat more subtly than Ryan's Objectivism, and perhaps the Big Sister doesn't really even subscribe to it, but a more educated philosopher might be able to point out the similarities in ideologies.
Religion also now seems to permeate parts of Rapture's life with the 'cult of Jack' having arisen after his arrival and absence in the decade between BS1 and BS2, something that Rapture didn't have before its fall.