What would other directors of yore be shooting if they were making motion pictures today? Would John Ford revive the Western or would he be making a superhero movie? Maybe in his hands The Lone Ranger wouldn't have been such a disappointment.
Would D.W. Griffith still be a racist, and what would he be able to contribute if someone else had already invented the language of cinematic storytelling before he did?
Alfred Hitchcock and Stanley Kubrick were constantly evolving and pushing themselves to new filmmaking peaks. Would they have dabbled in 3-D? Could Orson Welles have made anything close to Citizen Kane today?
Of course, all the classic moviemakers were products of their time and it is difficult to take them out of the eras in which they were born. We likely wouldn't have Charlie Chaplin's Tramp character without his pre-Great Depression immigration-to-America experience. Leni Riefenstahl made her propaganda films in Nazi Germany, so it is impossible to contemplate what she might have done elsewhere (or elsetime).
Frank Capra, Akira Kurosawa, Francois Truffaut, Ingmar Bergman, Federico Fellini, Billy Wilder, Sergei Eisenstein, and all the rest of the notable names in film history were shaped by the time and location in which they lived, so my hypothetical ruminations need to remain nothing more than fanciful daydreaming.
Still, it's fascinating to ponder alternate realities in which those specific filmmaking and storytelling visionaries were transplanted to the here and now. Imagine Noah directed by DeMille, or Star Wars directed by Fritz Lang, or some incredible, never-before-seen-or-imagined masterpiece directed by George Melies. The imagination runs wild.