There's probably 3 main markets propping up the CWL QR route.
1) UK-Australia/NZ travel - which as already discussed isn't likely to recover for some time. NZ especially have performed very well in holding Covid back, but are now behind most other countries in rolling out the vaccine as it initially wasn't a priority for them. It's unlikely this market will start to recover until at the earliest mid 2021, maybe even towards the end of 2021. It will then take time to recover to levels seen before. It will be interesting to see how Airlines respond to this, especially QR and EK. EK especially had a huge offering pre-covid, with many A380 flights each day from a number of different Airports. If EK don't restore their level of frequency to what it once was, QR could well benefit from the displaced catchments. I'm not sure on EK's position but I'm sure I've read somewhere that QR have no intention of bringing back the A380's any time soon.
2) UK long haul holiday market - Many CWL QR travellers were travelling on holiday to Asia, with Travel Agents also pushing holidays. People are itching to get on holiday but may now be more cautious on going long haul to more unknown countries. Whether those countries are ultimately safer remains to be seen, but the interpretation for the travelling public will likely be to travel to more well known places that may be deemed "safer". Fact and public intrepretation/cautiousness are two different things here.
3) Foreign students - Wales has seen a big increase in foreign students coming to take advantage of the UK education system. With the UK performing so badly in fighting covid, along with a very unstable and confused plan for education, this may result in lower demand for foreign students to come to Wales' universities just yet.
Without the combination of the above 3, i can really see the CWL QR route struggling to regain popularity, but hopefully QR remain dedicated to the route for some time.
It's worth noting we are now nearly only 2 months away from the route restarting again and it still being on sale. I think had QR planned to suspend the route for longer it would've been taken off sale by now. I think at this stage, the deciding factor on it returning is now the covid travel restrictions and lockdown restrictions over the coming weeks.