Ok, so, I'm getting over my tremendous shock at just having visited the Cuban government's website, http://www.cubagob.cu/,and seeing them list under Raul's titles: Primer Secretario del Comité Central del PCC (First Secretary of the Central Committee of the Communist Party). The PCC's website still has Fidel listed as First Secretary, though. So, take it as you will. I think it's further evidence that Raul is the one who is completely at the helm.
But to hedge my bets, I'm just going to call him the Third Secretary.
Here are the links: