I wonder if the Australian version will go ahead in South Africa. Or if they’ll move it to the UK site in Australia. Although the Australian version possibly goes out about the same time as the German version that uses the one in Australia but they’re likely to not use that set for the same reasons.
I think it is quite likely, and possible Australian Survivor will film in Australia now too having previously ruled it out. As the latter is unlikely now to get a series in the can in time I can I'm a Celebrity being pushed back to it's in-season February slot (it aired Jan this year), but as you say filming dates will be all over the place anyway. Ten had reversioned their Amazing Race to stick within Australian borders too but now state borders are closing back up seems unlikely that'll go ahead any time soon.
From ITV's perspective better to try and go ahead with something this year, especially with it being in the key pre-Christmas slot, than postpone and hope they could perhaps do a series next Spring, whether in Australia or South Africa, as nobody knows how the next year is going to pan out. I do think this could very much be on theme and work for the show, and it's in their favour there isn't really an established reality show based in a haunted house. It does fit the "Get Me Out of Here" theme.
Turns out nobody had 2020 vision.