I have a lot of problems with Halo 4, but it's still a quality game. 343 tried to add stuff and make Halo feel fresh, but ultimately hurt the game more than it helped. If all the same mistakes are made with Halo 5, then we can really begin to worry.
I think a lot of the stuff we complain about was added late. Look at the reveal video, it was much closer to the Halo game we want than what Halo 4 ultimately ended up being. No AAs, no armor mods, no annoying white text in the middle screen, BR Slayer rather than Infinity Slayer. I really think based on what little we know, Halo 4 went through some very troubled development. I think the fact we were shown so little up until after E3 was because they didn't have a solid final vision on what they wanted it to be.
Things we do know about development. 343 was building a studio while building the game, not an easy task. Ryan Payton, one of the more notable early developers to join 343, left in 2011. He was creative director if I remember correctly. Nathan Walpole, I think it was, mentioned on HBO one time that many early members of 343, left not too far after or something along those lines. We also learned right after Halo 4 released, the lead sandbox designer left 343 back in January. If we learned anything from Reach and Sage, it's that whoever has the position on a Halo game can make a huge impact and difference. We don't even know what else went on, but from what we do know, there were a lot of changes going on during development.
I also think 343 will take the feedback and criticism from Halo 4 a lot more personally and serious than they did with Reach, since this time it's THEIR game, and not Bungie's. We'll see whenever they reveal what is in store with the TU, how serious they are taking fans complaints. The plummeting player count is clearly a sign people aren't happy with the online multiplayer, they just aren't coming back. It's definitely not a sign people aren't interested in Halo, because sales have been fine, they just aren't maintaining those players. Halo 4 doesn't need major changes, it needs a few things to be tweaked, and more small maps. We've discussed those changes many times, so I won't cover those again. Hopefully we get news in the bulletin tonight on the TU, 343 really needs to do something to get the fanbase excited again.