I doubt it will happen. First of all, current companions aren’t all companions there are to be so 6 slots won’t cover all available companions anyway.
Having bigger party would also most likely mean 6 party coop, which is something Larian might now want to tackle.
It is still unknown with wide selection of companions will stay available fortune majority of the game, or if BG3 will follow D:OS2 formula and force you to pick 3 permanent companions after ACT1.
