Olympic 3G won't be a thing because gun regulations would basically mean that America would hoard all the medals all the games.
Some countries ban certain calibers such as .223. Others limit magazine capacity to a small amount of bullets. In most cases prices for both weapons and ammunitions are odiously expensive, which reduces an already tiny pool of competitors, automatically throwing it into sub-curling levels of popularity outside of America. Plus, good luck finding competitors in major countries with severe gun laws such as UK, Australia, Russia or China.
It. is. never. happening.