A scope will work fine. Iron sights might be a problem unless you have some kind of ambient light shining on your gun, which of course will illuminate you as well. However, hogs are notorious for their bad eyesight, so unless you are having a party with your ambient light, it probably won't effect your hunting.
For the kind of precise shooting you will likely be doing on hogs at night, I would recommend a scope simply because you can be more accurate, especially at longer ranges. Hogs rarely like to pose for a shot, and sometimes angles can be tough (like head-on and quartering away). You won't be disappointed with a good scoped rifle.
As for pigs being left, I wouldn't worry. They are taking over the country and I doubt you will have any trouble with population. Finding them may prove a bit harder, but the night hunting will help.
