From AirlineRoutes blog:
http://airlineroute.net/2014/01/03/cx-744-s14update1/
Update at 1625GMT 03JAN14
Based on latest schedule changes around 02/03JAN14, Cathay Pacific is moving forward planned Final Boeing 747-400 Scheduled long-haul service. Last Boeing 747-400 service to San Francisco is scheduled on 31AUG14, while Johannesburg service is scheduled on 31AUG/01SEP14. Note further changes remain highly possible.
The oneWorld member previously planned to operate last Boeing 747-400 Scheduled long-haul service on 25OCT14.
Following schedule is effective 01SEP14:
Hong Kong – Johannesburg
CX749 HKG2345 – 0625+1JNB 77W D
CX748 JNB1230 – 0715+1HKG 77W D
CX748 on 01SEP14 is scheduled to be last Boeing 747-400 long-haul service, based on 03JAN14 schedule listing
In August 2014, 747-400 operation on Johannesburg service operates on Day 57 from HKG, Day 16 from JNB