From what I've understood your MVP Sale Gold Pass will get you most/all of the benefits advertised to you at the time of purchase. All-Parks access, free general parking (except at Knott's), early entry to parks that offer it (excluding Cedar Point), and access to seasonal festivals like Halloween Haunt, Tricks & Treats, and Winterfest. The only benefits that may have changed for you are how All Season Fast Lane will work at other parks and that Haunt mazes will still be an upcharge.
Six Flags will hopefully have this all sorted out for 2027. I suspect it'll be the new system from then on; or until they decide that they still aren't getting enough people buying passes. I'm not excited that I'll probably have to buy a 2027 Prestige Pass for all parks access, but if that's what it's going to take then I'll probably do it.
Watch out when you go into the Six Flags app and look for your pass under non-Kings Island park pages. Mine is showing up as simply a Gold Pass for parks like KI, Cedar Point, and California's Great America; a Gold Pass Midwest Region for Chicago's Great America; and a Gold Pass East Region for Six Flags Over Georgia and Great Adventure. For parks like Canada's Wonderland, Carowinds, and Kings Dominion it only shows my 2025 Gold Pass under the "expired" tab. There are some parks that don't show my pass at all. The app shows people's Prestige Pass(es) across all park pages, just not Gold Passes.
I intend to reach out to Six Flags to find out more about this before my potential trip to Kings Dominion for their Opening Day. If I don't get a clear answer or get a different answer at the gate, I'm also preparing myself to have a nice and civil conversation with KD's guest services.