Another theory: Kylo Ren/Ben Solo will be redeemed and die killing the emperor for good, much like Darth Vader, but 'finishing what he started'
My biggest theory is Skywalker is the new 'Jedi' IE: force users will be named Skywalkers, a new order, lead by Rey, learning from the failures of the former Jedi Order(which strict rules, adherence to ancient dogma contributed to its marginalization and eventually downfall)
Yes i think it would have been better for the whole trilogy in general, if they had most of the overall story mapped out beforehand. Like TFA poses questions and plants clues and leaves threads dangling, that TLJ ignored, changed or flat out abandoned, which in itself was jarring. TROS then spent a lot of its run time ret conning a lot of choices made in TLJ. All could have been avoided if they had planned it properly instead of winging it.I didn't mind that palpatine returned or that Rey is his granddaughter, I just wish they had started planting hints to it in TFA and TLJ. It felt really forced with the way it played out