If I’m not mistaken they said there wouldn’t be neither a full replacement nor a support bassist. If they stick to this, well, I don’t have an opinion on whether this is a good idea or not.
I can see someone else replace Aoi (fully or as a support).
Losing Reita the way things happened is something different from how heated emotions seemed to be about Aoi that’s why I weren’t surprised, if that were four people on stage again but not five.