My theory is that BTS will finish their world tour, after that they will probably send some of the oldest members to the military and while they are doing their military service, Bighit will debut another boy group because then they have more time to focus on them and while the other members of BTS are in the military, the ones that are left will either continue to release songs together or maybe do some solo work. It could also be that BTS will stay together as a group until 2020 but you never know.

I don't know why this has so many down votes! BitHit NEED to debut a new group next year, I think some fans are under the delusional impression that they can just wait until BTS enlists but it just isn't that simple. New groups don't just start earning money straight out of the gate, that takes time. They need to debut the new boy group now so that by the time BTS start to enlist, the new boy group is already earning them money.