I doubt that DESO's are a dying breed.
Firstly there are limits to the cadet scheme. After >20 years the scheme only graduates about 40 Cadet's from flying school into the airline as S/O's each year. With the switch from HKG resident-only recruitment, to international candidates (with a connection to HKG), they will boost Cadet intake from 40 to about 60 per year. After interviews, flight grading and Adelaide, it's about 2 years before a Cadet gets anywhere near a CX flight deck.
With the exception of periodic hiring freezes (9-11, SARS, etc) annual recruitment targets have ranged between 120-200 per year. So basically, DE pilots are recruited in the expansion years.
With changes to the Flight Time Limitations system over the next year or so, it is likely that S/O's will be needed less for Australia and Middle East type flying. But ULH services to Europe and North America are likely to be expanding at the same time, so losses and gains will balance out.