You forgot the variable that if ethiopia collapses it could cause the worlds largest refugee crisis resulting in millions exiting the country to safer countries, and I doubt ethiopia will allow for a peaceful breakup only way it will happen is through war and even then the west wont allow it to happen, essentailly ethiopia is kept on life support indefinitely by the west and I dont see them cutting that off soon.
Think about it deeper. If their goal is to prevent war, loss of life and a refugee crisis. Then it wouldn't be far fetched to say that people will lay the case both internally and externally for a peaceful dissolution to avoid it.
Its gotten to a point that they see no other way. It will be offered as an ultimatum in the end, that's what i believe will happen.