The difference here is that 343 is working on a established franchise. So yes, I do expect them to use the sound files for the returning weapons and items. These changes are like changing the sound effects that play when Mario is powered up by a mushroom or collects coins or like when Sonic picks up rings. Those sound effects are iconic and distinctive parts of the series; of the experience.
I'm just going to disagree and leave it at that. There are plenty of sounds that sound like past games, and their are new sounds, which IMO, sound vastly superior to past games.
I'm not nostalgic to gun sounds, and let's be honest, no one is going to be harping on this a day or two after release.