I loved Halo:Reach but the only thing i didn’t like in the multiplayer (besides amor lock) was the point system. In Reach you would almost get the same amount of points wether you win or lose. I would join a game and people would not play because it doesn’t matter because they get the same amount of points no matter what. If they do have a point system in Halo 4 not a 1-50 i would hope that there will be a significant difference between winning or losing so people actually care about winning now.
So far, I think the Halo 4 ranking system will be like this: you play for an average amount of time and gain Spartan Points (new credit system),and you get these SPs from the amount of xp you get. You can earn more xp if you play better. So, if you are a newbie to Halo, you get less points than that of those who are better because they play longer. So, the better you play, the more xp you get, the more SPs you get from that, and the faster you can unlock something.