I doubt everyone is going to be permanently banned for many reasons but most of all because they want more money for map packs and future cod releases.
Everyone will be banned for as long as it takes for 3arc to figure out how to prevent modded eboot's to hack stats. Once that is done they will either reset everyone to their previous legit stats, leave them at their hacked level or a complete reset. If you think about it wouldn't make any sense for them to reset everyone and let them back on if they haven't figured out how to prevent the hacks in the first place everyone would just do it again.