At the end of the day, the fare paid by the "open-market" normal passenger who can shop around but still decides to fly with CX will hardly change as normal competitive pressure will reduce the base fare to match the fuel surcharge increase. Their variable surcharge amount depending on location seems to have (mostly) considered this already.
Where, however, the passenger does not have the ability to shop around, then the cost will increase - a few groups come to mind: A) the pax who may be locked in by some existing/overarching corporate arrangement/deal (and even here, this will get resolved at the next round of negotiations), B) pax using Asia Miles to redeem tickets, and C) CX staff travelers
There would also appear to be some tax/accounting driver in only applying the fuel surhcarge to incoming flight sectors (not only that perhaps HKCAD would not approve it ex-HKG) - the labyrinth art of tax minimization used by all international airlines.