Historical Note:
a) two of the three recanted
b) Mrs JB Gaillot, Jr. never did - if she is still alive today, she would be 96 years old.  She published a book in 1970 - God's Law - proclaiming that God supports segregation.  She refused to enter church for the weddings of her sons.
Your point about excommunication's impact may be correct but not in the context of 1950-60s New Orleans and the archdiocese of New Orleans.  It was very significant.
Rummel died almost blind; his co-adjutor returned from Rome and VII and continued to implement desegregation in the archdiocese.  That co-adjutor, Cody, would later die as cardinal of Chicago in his own state of scandal and intrigue.