What I want to know: How are they going to do Splatfest concerts if Callie is abducted in Hero Mode? How would that work for players who are attending Splatfest but haven't "rescued" Callie yet in the campaign?
For the fact that Marie seems to be spending her time in Cuttlefish's old spot loitering over the grate (and the fact that they're apparently unrecognizable to the new squid generation), my assumption would be that if Splatfests still occur, the squid sisters no longer preside over them regardless. Once reunited, you can probably just catch them hanging out in Octo Valley or maybe hanging out in the square to serve some other "postgame" purpose.
It's also obvious by now that they're no longer presiding over news updates, so how they opt to relay that information now will be interesting to see as well. Very few characters in this game seem to actually be directly taking on the same roles they used to have, and I kinda like it.