A subsequent release of the original was distributed by Warner Brothers, who have since handled all video releases, at least in the USA. They also produced the Burton/Depp version. So to answer the OP, I'd assume WB has rights to Wonka.
What I'd be curious to know is if the movie rights also include theme park rights, because while you'd think a ride would be based on one of the movies, perhaps an original ride based on the legend of Wonka independent of the movie's imagery is also possible if no one has exclusive theme park rights. Though I'd also figure the movie rights probably include all other forms of media outside of the original story/stories and in this case the line of Wonka candy.
So is there no possible way for Disney to acquire these rights, or at least the right to build a theme park attraction out of it? Because to me Willy Wonka is such a classic movie, that relates to almost anyone of all ages. An for some reason I always thought it was a Disney movie
But I always had this attraction in my head where the Que starts in the gumball factory, with the lollypop trees, and you get to feel the smell, and the aroma of everything around you. It could be really detailed to...
Then once you go, it could go through all the movie scenes that proceed the factory tour....
Personally I think an attraction like that could become an instant classic, and hopefully one day will come to fruition!