I personally think that not losing a rank when you lose is the worst idea ever. If you have something to lose (your rank) then it will keep people from going to visit the bathroom or anything else during a game because they will know they might lose the game and lose ranking. When there is no ranking system based on if you win/lose thats when people quit out of games more and quit playing for a period of time in between games because they know there is no consequence for it. If you didn't want to lose rank for losing a game in Halo 2/3 then thats what the social games were for, they didn't have a rank.
I do think it is sad to for me to say it but it really is true, if halo 4 doesn't have a ranking system like halo 2 or 3 then that will be the difference of me buying the game versus renting it (since all I do is play multiplayer and not single player). I played countless hours of halo 2 and 3 and still go back to halo 3 (and wishing I could go back to halo 2 to play online) because the multiplayer is competitive. I hate games like COD where all it takes to "lvl up" or gain more armour abilities is time playing, not skill. When this happens then you have a bunch of people with no lives that are the highest rank with everything unlocked because they have the time to play not because they are good. This takes all of the competitiveness out of the game because no one works together because in the end it doesn't matter if your team wins or loses just if you personally did well. I believe this is one reason that halo 2/3 was so good, it motivated people to talk and strategize with teamates and try and get a team together to go in and play. I also believe a ranking system helped match people of even skill up better, in other games just because you had a high rank didn't mean you were good so you would get matched up with people that just had time to play and not matched up against people who were of similar skill. I do think they did just fine in halo 3, they had the social matched for the casual gamer and the ranked matched for the competitive gamer. Yes the casual gamer is a big money base for them but I only think they are a money base for a while until the causal gamer moves on to another game, the competitive gamer is what will keep the game around.
I believe with halo reach they were trying way to hard to cater to the causal gamer way too much and they were becoming very similar to COD. I want a game that I can go in and play competively against other players with a reward for wining the game and a penalty for losing it. I just really hope that they realize that the ranking system in Halo 2/3 was what kept people around playing it for so long and put it back into halo 4. Overall I think it would be possible for them to do a combination of both systems so they can have the pointless "armour unlocks" and the such but still have a ranking system.