i hope not. as much as i love both xg and kep1er, the way xg is right now as a 7-member group is already perfect. maybe have hikaru on another group, or solo. i can't imagine lesser lines for hinata or the rap-line since she's a rapper too.
You dont watch the xg documentaries. Hikaru didnt make the cut for xg. They decided 7 members was the sweet spot. And they were right. None of the members would have any lines to sing. Look at bahiyih who only sings ad libs. Hinata only gets a few parts divided with harvey and maya and cocona. Add one more person amd somebody isnt singing much at all.