I (and lots of others) noted that traditionally that job, the number three post in the Government the King is Prime Minister and the Crown Prince is First Deputy, usually has meant that the holder is in line to be the next Crown Prince. Now, the Royal Court has made it official, formally naming him Deputy Crown Prince.
While not a surprise, there will likely be speculation about the timing. King ‘Abdullah is 89 (he is already past 90 in hijri years), and ailing; Crown Prince Salman, though a much younger 78, has had at least one stroke and may have suffered some impairment. (King ‘Abdullah's two previous Crown Princes, Sultan and Nayef, both died before succeeding to the throne.)
That is unlikely to be an issiue with the much younger Muqrin, born in 1945 and still in his 60s. He is, however, the youngest of King ‘Abd al-‘Aziz' sons to have government experience, and is believed to be the youngest still living. The decision to put Muqrin in line for the throne assures that the throne will remain occupied by a son of the founder of the state,as was the case with Kings Sa‘ud, Faisal, Khalid, Fahd, and ‘Abdullah. But after Muqrin, the issue of passing the throne to the next generation (some of whom are themselves aging and ailing) will be unavoidable.
Muqrin served in the Royal Saudi Air Force, as governor of Hail and then Medina, and headed Saudi General Intelligence from 2005-2012.