That's applicable to engines featuring DEF, but for the rest my theory is that they will just increase EGR to lower combustion peak temperature and thus decreas

That's applicable to engines featuring DEF, but for the rest my theory is that they will just increase EGR to lower combustion peak temperature and thus decrease NOx at the cost of engine efficiency. There's no magical software fix that can decrease NOx without affecting the combustion and thus either performance or efficiency. That would be the holy grail of thermal engine research!