Nothing much to add to this discussion really, other than it's been an interesting read!
I can't see the future looking too bright for DBGTROTD and would agree with @JoshC. to be honest... can't see that it will open in 2020 at all. It would take quite some retheme to change it to something else minus VR. It has been, and is going to continue to be, a huge problem for the park.
One thing I will say - and have always said - the show building exterior (generally), the pre-show, and above all else, the Victorian carriage exterior, the tube train interiors, the Underground station and the fake shop (minus the guy in the white t-shirt) are all pretty much world class - and I say that without a sense of irony at all. They've nailed those. It's just such a shame that the rest has always been a bit of a confused mess. Maybe that bodes well for keeping it and rehashing it to something else, I don't know. For it to be removed in it's entirity after the Derren IP expires, or before, would be unheard of - but I don't think it's out of the question. The money pot isn't never ending, and there comes a point where you have to admit defeat, especially with the added complication of coronavirus (and the very valid points about the storyline featuring corona symptoms, plus people probably not wanting doom and gloom when they can finally go to a theme park after all this has passed) - it's going to be morbidly fascinating what happens next.