A bit off topic, but I think the reason they can't film Survivor is because Fiji is keeping the borders closed. Theoretically the contestants and crew should be able to show up, isolate and film. But if Fiji won't give an exemption to let them on, then they have to do something they haven't done in years.... Find a new location and build all the game infrastructure to film a season somewhere else.
I think I've read somewhere that they are considering a US (Hawaii?) based interim season until they can get back to Fiji for a more 'normal' season, but I think CBS and Fiji are basically playing chicken to see who will blink first.
As for TAR, with vaccinations going out now, I could see them filming in the spring or summer maybe. That should be a point where vaccinations are available to regular folk in many locations, and we can start seeing borders reopening (with vaccination proof). So a new season might happen for Fall 21, but a more realistic expectation would be to see the new TAR season in Winter 22 at this point. We'll probably see 2 more seasons of TAN in the mean time, to fill out the schedule and to keep Phil busy.