You can't predict Bungie's actions. They may have been rushed in the process of Halo 2 and when Halo 3 came around they removed the Brute Plasma Rifle, but when they dropped ODST the Brute Plasma Rifle was found once more. So they can just pop it in Reach once more. They can also throw it in the campaign and only campaign like the Plasma Rifle. Since the brutes arn't a primary army they might as well just stick to regular covey weapons. They could handle neerfles, needlers, or just plasma rifles. Just don't get your hopes up because you know how to write multiple walls of text.