I would call it a fad actually. I mean, it’s the same thing that happened when DOTA2 and LOL became popular. We basically only had hero based games for three years or so. Before that it was Minecraft and survival games and after all this it was asymmetrical MP games. now the hot thing is PUBG and Fortnight! So yeah, it is a phase and the only reason why BOIV did it, it’s because right now it sells.
(S_orry, it’s BO IIII!!! damn I hate that title. In Italy we have the term “bimbominkia” to describe kids and posers that write like that. My mind always goes there when I see it._)
Sometimes a bunch of games will survive the hype phase and stay relevant a long time after the fact (LOL, Overwatch, Minecraft, I’m sure PUBG will be the next one), the clones however die out. With all the server and MT issues COD seems to have right now, I’m not sure it will stay relevant. If Halo would have done the same, and that even further down the line - release date is still far of - it would’ve zero chances to become popular. The IP is not as relevant as CoD anymore, so it can’t risk to follow old trends like the competition did.
That said, and I repeating an old comment of mine here, the mode would be perfect for Halo! Think about it: orbital drops as spawns, open spaces, Halo sandbox and vehicles, Covis and Flood as AI enemies on the field, Phantoms dropping bombs and goodies on the field, giant UNSC space ships entering the atmosphere and moving props, players and bodies around just by pressure force and all this while the is getting glassed from space or by giant Scarabes outside of the playing field. Tell me it doesn’t sound awesome!
However, a mode like this would be expensive to make and resources in development are limited sadly. Not to mention 343i has to prove me they can make a good Halo game before that first and foremost. Sorry, but everything I liked about Halo in the last seven years or so was made by someone else (SPV3, H2A and HW2 if you’re curious), that’s not a good sign! Therefore I’m actually happy they’re not wasting time with BR modes.
Even if the cynic in me believes 343i is not doing it for the reasons mentioned prior to this and not because they won’t follow trends again… Let’s see! 
They should give us the option to make a mode like that in forge though. I’ve seen similar concepts since Reach anyway, so it’s not even new. If it gets popular down the browser road sure, develope a full blown out mode over a year after release or so.
great way to piss people off. What will Halo sacrifice for it if they choose to add it?