Geh065,
It is more about volume than weight for regional sectors. For this reason, I believe a conversion program will eventually happen. However, the 400 BCFs have been a disappointment performancewise. So CX is probably skeptical about investing heavily in another BCF program.
I believe eventually there will be a conversion program too but not in the next few years. The investment aerospace companies need in order to launch a program like this requires both a market for the freighters and planes to feed the market. The demand I suspect is there already but there are no spare 777s to feed the market at the moment. The only 777s on the market have been the CX 772s and some Singapore 777-200ERs and 777-300s. Certainly not enough to feed a BCF line.
It is for this same reason that the Russian/Airbus joint venture to start an A320 conversion line was scrapped, and there are certainly a lot more spare A320s then 777s but obviously still not enough. The first A320 had even arrived at the factory already for conversion!
Unless there is a major market downturn that bankrupts a major 777 operator, I don't think we will see a conversion line for at least nearly 10 years.