It's a bad theory. For one, the timeline means that Qi'ra gives birth to Rey when she's in her mid 40s, which implies that Qi'ra survives this new series of movies, and spoilers, she's probably not. There's a reason Han is so miserable in A New Hope compared to his perky, happy-go-lucky personality in Solo, and it's probably not that Lando figured out a better way to cheat at cards. There's also the fact that, oh right, The Last Jedi explained that Rey's parents were actually garbage people who traded her for booze and space crack.
It's not like this theory -- and the many, many, many like it -- are any better from a storytelling perspective, either. The whole point of Rey is that she's a complete rando who finds herself possessing powers that she previously thought were based in myth.