I think 99% of the comic book mythos do crumble without the main character as they are the core of said universe. That said, if a universe is developed enough, it can become it's own thing indepenent of that character. The most obvious example is the Spider-verse... Sony is creating an entired shared universe without Spider-Man. So it's possible. Batman is another example. We see plenty of Batman related movies and shows without Batman actually in it. Birds of Prey, Joker, etc.
The question then is whether or not the world of Wakanda is at the point. It's not as developed as the Spider-verse or the Bat Family, which have obviously had decades and decades to flesh themselves out. But can in theory survive without the actual Black Panther. Is there enough there? Probably too soon to tell... though in the case of the MCU at least, marvel has enough of a track record to where ANYTHING they do will likely suceed at this point.
None of which means they HAVE to do anything without T'Challa of course. We're just speaking hypothetically.