Meh, it’s really just speculation from deleted footage from the first preview, which did show an older Kasumi/Misty. But there is a lot of off the wall shit that was thrown around too; apparently the movie was going to be the definitive end of the anime, Pokémon weren’t real, 10 year olds are considered adults in that world, etc...
None of that makes it canon of course, although many treat it as such for whatever reason