Just spoke to the person who runs the fan page for the Thriller / Tsunami coaster on Facebook. The coaster has not been scrapped yet, and it might not be its end:
As of 21st March 2020, the track is still on site, if you look at Google Maps.
I was thinking of going to go to Thorpe Park on 6th July, but, at the moment, Fastrack doesn't seem to be available, which I need because I struggle to queue. But with the reduced capacity, do you think the queues will be that long?