Of course there are still languages where you use a different form according to whether you are speaking to a man or to a woman, or to a "superior" or an "inferior". I think it's as well that it's all been whittled down in Standard English. It's a puzzle enough in French, I gather, at times, knowing when it should be tu or vous.
I can envisage the same kind of thing happening to the third person pronoun too - in fact it's already happening.
The singular third perspon is gender specific, and the plural isn't, so you find people saying they quite often when strictly speaking it should be he or she. The move from thou to you was a way of sidestepping class differentials, the move to they is a way of sidestepping gender differentials. Same process really. It's a very clever language we share.