A look at military wounding and death statistics shows that small arms injuries to the extremities are rarely fatal, whereas wounds to the head, neck, or torso are frequently fatal, which suggests a few things:
First, that improvements to helmet design are at least as pressing and as important as improvements to body armor systems. The current combat helmet does not provide adequate protection from blast wave exposure, which is the primary mechanism of injury today, and is sure to remain a dominant mechanism of injury long into the future.
Second, given the overwhelming preponderance of fragmentation injuries, especially to the limbs, improvements in soft armor materials and systems, guided towards improved armor coverage, are of key importance. And, of course, technological improvements in this area will also result in better, lighter hard armor plates. This may also reduce the casualty burden associated with small arms wounds to the extremities, which are apparently fairly common but do not result in substantial morbidity.
Further, with the data from OIF and the data from Gofrit et al, it would seem that the overwhelming preponderance of bullet injuries are anterior — that is to say, when bullets strike, they are 10x to almost 20x more likely to enter through the front of the body. It may make sense to consider pairing a larger and heavier armor plate in the front, with a smaller or lighter armor plate in the back. This is indeed quite an ancient practice — one which Alexander the Great was known to promote — and was recently employed by the Soviets.
More data is required, but, though admittedly unorthodox, this doesn’t seem like an obviously bad idea; full body armor does not exist, and one must prioritize coverage based on (a) where shots are likely to be particularly damaging or fatal, and (b) where shots are likely to hit. If shots in the back are indeed that uncommon, it stands to reason that the front armor plate is vastly more important than the rear armor plate, and should be made larger, stronger, etc., whereas the rear plate can be made smaller and thinner. That they are of equal weight and capability seems unreasonable, given that one may be ~10-20x more likely to be impacted than the other.