Chessington is (meant to be) seeing a £60m worth of investment over a 5 year period. When exactly that started I'm not sure, but obviously Project Amazon represents a good chunk of that. I believe there's also talks of more accommodation coming, which could also be included in that.
In any case, the investments such as Croc Drop, Rainforest, etc were all rather cheap.
As for these other rumours...
-I would not be surprised to see Pirates' Cove receive some attention this year. It's an area which is largely forgotten about by the park, and come 2023, will be adjacent to a brand new, very popular land.
-I guess it's possible that the park could get some (cheap) new rides in the area...but presumably we'd have seen some sort of planning application now? Unless they're temporary things...
-I see no rhyme or reason to remove Scorpion Express, and would be surprised if that happens any time soon.
As for Rocky Express, I don't see why the park would get it. As it stands, it's still not in any way confirmed that it's leaving Thorpe of course. It seems very likely based on the rumours, but I've heard it's still not 100% confirmed...
As for Tomb Blaster changing back to Forbidden Tomb / Terror Tomb or whatever. I don't see it happening. I'll gladly eat my hat if it does.
BUT, let's say the park do go about doing stuff to it and change it to an older name. Will the ride be any good? Probably not. The "refurb" from whenever it was (2020?) was dire. The new audio and story is appalling.
If they were to scrap the guns and bring it back as Forbidden Tomb, there is in my opinion no reason to believe that the park could do anything with it to actually make it in any way a decent ride experience.
Again, very happy to be proven wrong, but with the state they "refurbed" it to, there is no reason to believe that any future work will lead to any worthwhile improvements.