From a musical point of view it was clear that 15BO was a definitive signal that group should split with Carl and Dennis doing their own things or create something new together, maybe with some occasional involvement from Brian. Mike and Al would probably then invite BJ back into the group and add a few additional members and continue as the Beach Boys for touring and recording purposes.
I think Carl and Dennis would agree to this arrangment due to the revenue they would be entitled (unless they sold off their claims). In any case they needed the cash to prop up their affluent lifestyles, which to begin with would probably not be supported by a non-Beach Boys venture.
As Mike Love and Al would drive the "new" Beach Boys into MIU and Celebration territory, it's without doubt that they would publicly clash with their ex-bandmates who would probably deride the new direction and sound. This would probably come after Mike Love initiates the jabs with his virtue grandstanding and drug references (which he still brings up incessantly - like we know it ruined Brian's life and took Dennis'. Thanks for bringing it up as if those two men never accomplished anything else).
It would be a clusterfuck, but it might lead to more exciting work from Carl and Dennis and maybe they would learn to accept not being in the Beach Boys and forge a new and interesting path