BTS will most likely have to enlist without any special treatment.
There were talks that BTS, as the forerunner of the Korean pop culture, should be exempt from the army, similar to how medal winners from the Olympics are treated. Currently, all Olympic medalists, gold medalists from the Asia games, and up to 2nd place winners of international arts competitions can be exempt from the military by taking 4 weeks of basic training, and then doing community service.
While there were talks of change for the U-20 team that ranked #2 in the international games and for BTS, it looks like the current standards will stay the same for now. One of the reasons why is because for BTS to be exempt, the standards would have to be very ambiguous, and enforcement could be very difficult.