I'm glad I put up the pictures from the front that looked almost normal, so much can happen in 4 days.
I think they knew exactly they're doing before they announced anything. I can also imagine a discussion, they can have the mountain and maybe a flat ride in it, or another coaster, but not both, too expensive.
I did think the way to reuse the mountain would have been to not put anything "inside" it. Around it, over it, a little through it, but mostly not. It would have been a compromise, but I think it would have been better to theme the mountain as solid not hollow for a coaster anyway. Nobody seemed to be able to grab the idea of thinking outside the mountain though.
They might still keep the queues, shop and lagoon, after all a queue can be used for any substantial ride and it's even the right height for most coaster load platforms though not the one it served. Thus the careful severing of the queues from the mountain. The waterfall piece behind Scrambler looks to have been seperate in John's latest shot.
As to something Dinosaur's Alive-ish in the spot and a coaster in DA's spot, the latter is fairly natural still while Volcano's is very much not, so I can't see that happening.
There is a picture floating around, e.g.
https://themeparkreview.com/forum/viewtopic.php?p=1905216#p1905216