Fellow blogger Angelo directed me to this article using MGM's musical adaptation of The Wizard of Oz as an example of how copyrights have been extended. According to it, the MGM film has a little over 20 years before it enters the public domain.
To be honest, the imagery of MGM's Wizard of Oz, whether you believe they correctly reflected Baum's vision or not, has undeniably entered our culture so completely that it's almost a surprise it's not already public domain.
But really, when 2035 hits and the movie is public domain, what's going to change? Unless another widespread movie version comes along that makes people forget the MGM film (HIGHLY unlikely!), it seems it'll still be loved. And while anyone could make a DVD/Blu-Ray/whatever we'll be using for video then, or a piece of merchandise, it's not guaranteed it'd be of high quality. I'd imagine Warner Brothers still doing video releases, or even claiming people can't use their video transfers of the film, because those transfers are their property. (And considering the price tag these transfers and restorations have had, I couldn't blame them.)
It's like many silent films now. You can get Douglas Fairbanks' The Thief of Baghdad for free from Internet Archive, but the really good version is only on DVD and if you want that, it's not the cheapest one out there. Same for other silents as well. And since these prints have been restored and have new scores, they do own a copyright of their version. We could very well see the same treatment for Oz.
Now, it's possible that Warner or a bunch of studios could press for another copyright extension, but as the article states, a 95 year copyright term is long enough. The copyright will (don't hate me for saying this) last longer than anyone who worked on the film. Even though Warner Brothers should be commended for their handling of the film, they only own the rights. They didn't make it. In a way, it isn't "theirs."
So, where will MGM's rainbow be in 2035? Most likely still out there, still bringing smiles to generations.