If the Wikimedia foundation lost their .org domains, not only would they need to find a new domain, but they wouldn’t be able to redirect requests from the billions of links to Wikipedia on the internet, and all those links would die.

I also don’t think that will happen. If the new .org owners took down a world-beloved high-traffic site like Wikipedia, the public outcry from people of all political persuasions would make government regulation of the domain become quite likely and I’m pretty sure .org’s new owners don’t want that smoke. I also don’t even know the rules, it might be impossible for them to do so for some technical reason.