Assuming copyright laws don’t change by then, otherwise there is no way to know.
A plausible answer is 1977 (when the film was released as Star Wars) + 95 years (for pre-1978 works) = after 2072. However, the film had been edited by George Lucas for the 1997 “Special Edition” release. Does this mean that I cannot publicly play the Special Edition VHS tape I have at home in 2073 and have to wait until 2093, or perhaps 70 years after GL’s death?
George Lucas has been infamously attempting to erase copies of the original movie. Therefore, no HD home video release for the 1977 film exists, however, a fan effort known as the “Despecialized Edition” compiled different versions of the movie from various sources, patching the Special Edition 4K Blu-ray rip to try to replicate the original 1977 experience. Does this legally questionable version enter public domain in 2072, or does this only apply to official (SD) releases?
Anyway, the Despecialized Edition project as well as George Lucas’s treatment of the originals is an interesting rabbit hole to delve into for any movie nerd.
The despecialized edition uses a ton of cleaned up shots that don’t change in a story sense but have grain and wires and other compositing errors cleaned up. These are new works. Even the VHS release and any HD releases could be considered new works as the colour and sound would have been tweaked for each format. The best thing to do would be to find an original film print and have it scanned. Anything else would push the clock back.
The 4K77 project did just that, scan and color correction to reverse fading, and effectively no other processing so they cannot claim copyright. Arguably, Harmy’s Despecialized Edition cannot either, even if the original becomes public domain, as it could be argued that their effort only served a technical purpose. I don’t think you can scan, upscale and denoise Steamboat Willie (Walt Disney, 1928) and claim copyright on that even if you do it by hand.