Kammala jumla mai zuwa: A ranar 20 ga Maris, 2015, Vatican ta ba da sanarwar cewa duk da cewa ya kasance memba na Kwalejin Cardinals, O'Brien ba zai yi amfani da hakkokinsa ko ayyukansa a matsayin kardinal ba, musamman jefa kuri'a a cikin papal conclaves; ya gafarta kansa daga shiga cikin
Kotu ta shekara ta 2013. O'Brien ya mutu bayan faduwa a ranar 19 ga Maris, 2018, kwana biyu bayan cika shekaru 80 da haihuwa.