Its a very special person who takes on the daunting task of succeeding SAF. A proven track record of success at the highest level must be a prerequisite. I'd add to that by saying he has to have a very strong personality as well. Those two requirements rule out most including Moyes. Mourinho ? He certainly qualifies on both counts but will he come and for how long ?
Provided no interference from the top comes in like at Chelsea, I'd say a fairly long time. It'll be his longest job in football, no doubt about that.