I think right now there are two overall issues surrounding this franchise. I'm putting them in order as well:
1. There is a bit of Y-2k type unrest going on at the moment. It is a new console generation, so there is going to be a shift in the gaming landscape, some players leave, new players show up, ages are far different from the beginning of the last gen to the current gen (9-10 years? wow)... As such, games that are starting with a whole different world view have the potential to blow gamer's minds with things we haven't seen before, if they deliver like they promise. There are many games coming out in the foreseeable future that could possibly take the mantle away from call of duty. On Xbox360 the numbers seem fine, but on xbox1 there were about 35k people online tonight, the numbers are dipping and it's strange as to why, but then again maybe it isn't. There have been severe connection issues, patches and more patches that only an Xzibit meme could appreciate, and some of these upcoming games just seem like they are the golden children of Xbox1's future, COD no longer seems to be that now. This is the part that's out of COD's control, except for anything Activision could do, but they are pretty much hoping that Destiny becomes the wave of the future. And, as a MMO style game, they are hoping for players that commit COD style amount of time into this game, they are pretty much cannibalising their own mega franchise.
2. The game itself seems to have a lot of disapproval by all sources. I personally love this game, because I bought in to how this game plays and excel at it. But, it clearly has fatigue in the media, and players seem to snap at anything that isn't "balanced." I understand when basic fundamental issues screw the game up, like the dual 1887s or one man army noob tubes (lol), but when pretty much everything is deemed underpowered or overpowered there is an overlying issue. The formula is so similar each year at this point that A. everything gets compared to everything within the game as well as previous games and B. the players expect (and maybe should at this point) for these COD developers to have gotten "balance" figured out by now, its been about 8 years with this formula.
So, while I may disagree with most of the people (just overall, not necessarily the specifics) that complain about something being OP or UP, I feel like many people are just ready for a divorce from this game. These same players are the ones that I still want in the community, regardless of their individual opinions, because I need a large population to play this game and for it to be considered "worth" playing. The other crazy thing is that, this game has one of the most peculiar fanbases in gaming history, in that, most would consider themselves "casual" gamers that only play this game for specific circumstances. Some play because it's more like a sport than a game, because of the competition, because they had friends play which got them hooked too, because it's one of the few "moderately cool" games to waste alot of time on, etc. Therefore, the population of this game could plummet exponentially at the drop of a hat, if things play out a certain way. If the population on Xbox1 dropped to 20k, it would drop to 10k, because people would see their favorite gametype has 100 people in it and would then quit themselves as connections got worse and finding lobbies got more difficult etc.
As well as I generally do in this game, I also hope one of these new franchises really takes off because it would either allow me to go to the new "best" FPS community, and/or it could really give the franchise the wake-up call it needs. I know COD would never just disappear, because it's always had a Campaign, but it's very possible the juggernaut could end depending on how the next year plays out.