As of right now, we have no idea what the UNSC or Covenant’s involvement in Halo 4 will be. They could be major players or they could only be referenced a few times, we don’t know. We can only speculate and guess what weapons and vehicles will be in Halo 4. One thing is for sure, though, we will see a lot of Forerunner technology in the Reclaimer Trilogy.
Without knowing the UNSC’s involvement in Halo 4, it is likely that we probably won’t see many of the weapons that were in past Halo games. That’s not saying there won’t be new models of old concepts such as the DMR > BR > New UNSC “Rifleman” weapon", or the assault rifle series.
In actual human history, technology advances greatly during wartime and even during post-wartime, both offensive and defensive. This can also be applied to the Halo universe. Since the end of the war in 2552, it is a canonical fact that human technology has advanced greatly in the post-Covenant-Human War era, as proven in Halo: Glasslands with the UNSC Infinity, a new ship that incorporates Forerunner, Covenant, and UNSC technology.
I wouldn’t be surprised if the reverse-engineered Covenant energy shield technology was somehow mass-produced for the average soldier in the UNSC, either. But that’s purely speculation.
We do know, however, that a new model of the iconic Warthog will be in Halo 4, as shown in Forza 4. I think it’s also safe to assume that other UNSC vehicles have gotten some sort of upgrades since the end of the war. With humanity at it’s weakest, the drive for stronger offensive and defensive capabilities is stronger than ever, and without the looming threat of an inevitable attack by a far superior force, the unstable peace time would allow for new weapons and vehicles and other technology to be developed.
So I think it’s logical to assume that there would probably be a new model DMR/ BR, or assault rifle.
Can’t exactly say the same for the Covenant, or at least the Sangheili. It is common knowledge that the Covenant assimilated member species technology, and that the Prophets developed the weapons that incorporated Forerunner technology (Cole Protocol). So without the Prophets and the cohesiveness of the Covenant to develop weaponry, the Sangheili, at least, might have a difficult time developing new technology.
But considering the Sangheili are, like humanity, a very war-focused race, they might be able to develop technology for themselves that is unique to their species.
Now, given John’s predicament in Halo 4 and without knowing the extent of the UNSC’s involvement in Halo 4, I doubt we’ll see many UNSC weapons in that respect. The Dawn is wrecked and unless the ship’s armory was located in the aft section floating toward the Forerunner planetoid (and even then, assuming they haven’t floated out into space), there’s probably not many, if not any, UNSC weapons on the Dawn.
Then you have to consider the fact that concept art as shown the Dawn crashed.
So considering all this, sorry BR-lovers, your beloved weapon probably won’t be in Halo 4. Even if it was, it probably wouldn’t be the same as it was in Halo 2/3, then you have to take in possible mechanics that might affect how it performs. Then take into consideration weapon balance and etc…