I do not believe that there is any Connection between Bolvar and Deathwing, but knowing Blizzard this will not be the last we see of Bolvar (Notice the Ner'zhul skin?). He May reappear any time, as we understand it the people of Azeroth believe the "lich King" to be dead, but as there must always be a Lich King, Ner'zhul May indeed drive Bolvar to corruption.