This is my theory:
1) Whitebeard, kaido, big mom will not kill Rocks since they respected him
2) So thats wht only Roger and Garps teams up to kill Rocks
3) or Rocks give order to his crew to leave the island
So everyone is preparing for final wars .thats why Holy Knight trying to recruit other knights because they have to fight Revolutionaries dan Pirates ...
Personally i think shanks know the real identity of gomu2 no mi . Thats why he stole it.. when luffy ate the fruit shanks probably want to see luffy to awakened the fruit so he can manipulates luffy to give him One Piece