Now BTS has nothing more to prove in the mainstream, I do expect its music will go more experimental.
BTS snubbed in the Grammys means no matter what it does it won't be accepted in the mainstream.
There is the famous example of IU, who was given the Lifetime Achievement Award at MAMA when she was 21, and on 2015 she answered it with Chatshire, which has been her most experimental and provocative album of all (although it remains to be seen what the upcoming album might contain).
From 2015 Lee Jieun had taken over all directorship of her own albums, so it was her decision to become provocative, to say 'f you' to the KPop establishment.
Most of the flak went to her b side song Zeze, so her title Twenty Three was attacked less.
Still, the attack on Chatshire was so severe that she did not release an album on 2016, and returned with the mainstream ballad Through the Night in the spring of 2017, for which she was given a Grand Prize from Golden Disk (but still none from MAMA for which she is not eligible for a Grand Prize to this day).
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This snubbing might lead to a provocative album from BTS, followed by the military services of the older BTS members, and a brief opportunity to release a new album on 2023 followed by the military services of the younger members.