The Dubya said:
Tom Hanks...playing WALT FREAKIN DISNEY...telling the behind the scenes of one of the more beloved Disney films "Mary Poppins", i.e. Hollywood gets it chance to pat itself on the back for how awesomely awesome they are...
GEE, I WONDER WHO'S GOING TO WIN BEST PICTURE AT NEXT YEAR'S OSCARS. THIS IS GOING TO BE SUCH A CLOSE RACE.
Actually, that it really CAN'T entirely be that story is why it's an interesting (prospective) film. There are a metric-ton of "Walt: The Great Man" stories to tell if you want to deify Disney, but the production of
"Mary Poppins" is rather notoriously NOT one of them, even if the final film is (rightly) regarded as a genuine classic. Even with a light touch, anything other than a complete fabrication of the events will yield a story that is (at least in part) about two exceptionally driven, headstrong, nigh-egomaniacal artists - who both maintained paradoxically classy/whimsical public personas - trying to out-game one another over a movie project.
P.L. Travers was a hell of a character: Classic "childhood trauma/iron-willed adulthood" British author background, "brainy scrapper" reputation as a younger scholar/author (she didn't just want to out-write her mostly-male fellows in the British literary/poetry scene, she could out-drink them, out-party them, paid her earliest bills writing "erotic verse" and was no slouch with the ladies either) and also kind of a basket-case as an adult: http://www.dailymail.co.uk/news/article-2128544/Mary-Poppins-New-film-set-reveal-truth-creator.html
Disney, on the other hand, was basically Willy Wonka (Gene Wilder version) sans the last-minute "just kidding!" Meticulously cultivated his "magical grandad" routine in public, utterly ruthless and cunning as a businessman and filmmaker. He and Travers were both utterly unimpressed with one another, which drove both of their egos mad. I'm honestly perplexed at how the actual movie can be anything other than either a one-sided account (i.e. making one of them, probably Travers, the "good guy") or a dark-ish comedy about the absurdity of two adults going at it like wolverines over a fanciful children's film.