My previous post was written to clarify that I believe CX is seriously considering the 787-10 as an A330 replacement and that it is not too small as it is in fact larger than the A333.
If (and its a big if) CX are looking at something with about the same floor area (seating capacity) as the A330-300 to replace the existing aircraft, the contenders are the 787-9 and A330-900. The 787-10 is indeed larger than the A330-300, it is a little smaller than the 777-200 and A350-900.
The first question, do they need a 777-200 size aircraft to replace the A330-300 fleet (they are for the A340-300s) ?
The second question, why would they order two aircraft of the same size i.e. A350-900 and 787-10 ? What are the operational advantages adding an additional type with a small fleet of 787-10s with all the disadvantages of a new type (spares, maintenance, training, simulator, crew, rostering)?
The third question, if CX are still taking deliveries of new A330s in 2014/15, 22 A350-900s in 2015/16, and 26 A350-1000s in 2018/19/20 when would CX be looking at needing a replacement for the A330-300, and what would they need ? The A350s on order could easy cover the replacement of the A340s, 777-200s, and 777-300s and probably also some of the older A330-300s. The current fleet average for the 777 and A330 fleets is around 7 years, if they dispose of the oldest A330s 1 for 1 as new A330s are delivered this year and next the fleet average will drop to around 6 years in 2015, that is still very young.
The fourth question, when could CX get delivery slots of 787-9s or 787-10s, and when does this match when they would need the replacement aircraft ? Boeing is still well behind on the 787 delivery schedule, the ANZ 787-9 delivery was almost 4 years late.
If they need additional capacity, it would seem logical to convert existing A350 options, and move A330s to KA to decrease their A330 fleet age (almost 15 years average, compared to around 7 years at CX), and dispose of their older A330s. It would then be a question of what fleet would KA need to replace the A330s, and that would probably be for delivery slots in 5-10 years.
I would have thought the next purchase decision to be made would be what to do with the KA A320/A321 fleet, they would probably need new deliveries in the next 3 years.