There is a tool on GitHub that uses Claude AI to decompile practically any program. Adobe programs have been decompiled, and free versions based on them have been released to the public—with many claiming they even offer improvements over the originals.
On X, people are already showcasing projects that decompile PS5 games to run natively on PC, as well as games from other platforms running directly in the browser!
So, to answer the topic's question: yes, I believe it is just a matter of time and dedication before the TW engine is decompiled and its inner workings laid bare, allowing anyone with the right knowledge to implement whatever modifications they want...
Is it legal? I don't know; as mentioned earlier, this falls into a new gray area where—in the vast majority of countries, at least—there is no existing legislation.
Another thing: TK himself seems to have abandoned that engine; he could use AI to evolve it with very few resources and put it up for sale on his site.
After all, he apparently complained about lacking the budget to update the game because it would require so many man-hours.
With AI, there would be no excuses—it would be fast and cheap.