This is a really long shot, but how about this:

It was said, that there are (were) 4 noble families, 4 cornerstones of soul society. It appears that there is only one left (kuchiki). Thats why Byakuya is saying - if I won't follow the rules who else will follow them.
This could mean that the rest (so far we know that 2 of 3, yoruichi's family and shiba (dead kaien, ganjo and his one handed sister) are living outside of soul society, living in exile).

It might be that the 4th noble family is Kurosaki.