ab9898, your flight is a small number of days off, so it's way too early to suggest what will occur. You may have a troublefree trip with no delays. The QF A388s fly to DFW, DXB, LAX, LHR and currently HKG with the base in SYD, although MEL schedules also feature these aircraft to DXB, LAX and LHR. Revisit this blog a day or so before as a guide to what may be occurring, but as with any transport operator, problems can occur at short notice. At other times, as you imply, delays 'compound.'
At times when there are significant delays QF has been known to terminate a flight ex MEL in particular at DXB and not run the DXB - LHR - DXB sectors but as we saw most recently, it can also switch 'what forms what' in LHR depending on the tardiness of each incoming flight, the QF1 or the QF9.
It will try to get you on your way as expeditiously as possible but it cannot control the weather such as fog in DXB. Breakdowns such as has occurred with the allegedly defective fuel sensor of aircraft VH-OQF are a separate matter, but I can't think of any reasonably sized transport operator - air or surface - that never has a failure in service.
The media (Fairfax) has now picked up on how Alan Joyce took the 'earlier' (delayed) QF2 from DXB to SYD. Not a great look, irrespective as to whether he did or did not occupy a seat that would normally be available for paying (non staff) passengers:
Qantas passengers bound for Sydney stranded in Dubai on New Year's Eve