Not now and not in future either - he is already too old for that. I do suggest a bowler as Captain for PAK team, so that batsmen can play without extra pressure but Abbas is still too raw. At one point long back I won’t have opposed Asif as Test Captain but not Abbas or Yasir.
For the time being Sarfraz must take team to SAF - if he is to be dropped, then it should be in the form of “injury” and the deputy can take over on temporary basis. Otherwise, I don’t think it’s fair to the newly appointed captain to take charge for such a tough tour. PAK’s next Test is after WC and Sarfraz might come back again for 2 more years if new captain suffers heavy losses in SAF which will be a disaster- disaster situation.
Sarfraz must lead team in SAF for all 3 formats and then there can be a proper assessment if he belongs to WC plan or not. I think, after SAF, he himself will resign from Test captaincy while he isn’t doing that much damage to T20 side, where all 11 players are not needed in a 20 over game - performing 5 bowlers, 3-4 batsmen & a WK to do the first baseman’s job is enough, so Sarfraz can be hidden in T20 XI as Captain till 2020 WC.
Most complex problem is ODI - 5 months before WC, ideally one shouldn’t change the captain, specially when there is no readymade one at hand, but in WC, PAK can’t go with a dummy hand in playing XI and when there is a back up WK performing tremendously. So, SAF ODI should be last cut off time - if Sarfraz can survive, he should lead the side in WC, other wise new Captain should be given 10 hard fought ODIs against Aussies & Poms to prepare for WC (and Sarfraz out of squad - continuing sacked captain in squad isn’t a great idea, it suggests his failure as leader, rather as player).
In SAF, I don’t bother much about team results, as long as they are fighting every game but Sarfraz must not hide behind team. Even 0-5 is acceptable for him, if his own performance is good, because I don’t think there is any genius waiting - Sarfraz isn’t the worst Captain for LOs among availables; we have seen Misbah & Azhar. I wish, they don’t replace a specialist Captain with another one (Read MoHa) for WC. I would like to see Amir as deputy for ODI leg and preferably lead 1-2 games in SAF while Sarfraz is “rested” for Rizwan to keep.