I do wonder a few things, firstly, it's interesting to adopt the Six Flags brand (even if it's more recognizable) because of very low public opinion.
I'm also intrigued to see how this shapes out. Do they try to offload their weaker parks? Both brands are bringing in low-tier, rarely invested parks.
It'll be interesting to see how certain parks (like Six Flags over Georgia) compare to others in the chain. Carowinds is the closest park, but I doubt they compete over the same audience much, so it'll be interesting to see how a park like Carowins (which has gotten a lot of investment) stacks up to the combined investment pot. Then in the cities with two parks, do they try to make them like destinations, bundle park tickets? Or do they make one their premiere park while neglecting the other, Very intrigued to see how it all plays out.
Apparently they have said that they don't necessarily intend to just give every park SF branding, but apparently they feel it has value as a recognized brand. CF was a brand basically only known to niche enthusiasts, so I can see why they'd feel an obligation to keep it around in some capacity.
Parks will definitely close as a result of this (this next year will almost certainly be CGA's last season if this goes through, but others too).
Carowinds and SFOG are too far apart for most people to consider them to have an overlapping audience-I'm not even sure there would be that many people would be interested in that combo ticket. 20 years of this hobby has taught me that for most people, known parks that they're interested in boils down to, with only a few exceptions: 1) Disney, 2) Universal, or 3) their local park. Occasionally you'll get a Busch Gardens, a Hersheypark, or a Dollywood, but otherwise, most people simply are not interested in driving hours to other parks when they have one within an hour or so that is a known quantity, whether or not it's one that's much good.
I'm not sure the antitrust will agree, but the argument could be made that there aren't that many parks that have overlapping markets, or that have markets where the overlap of people who would realistically visit both parks is high. The reality is that many people who would go to Knott's wouldn't go to SFMM and vice versa because of traffic/distance/etc. Knott's and SFMM are the closest parks to each other at ~1 hour and 10 minutes away without traffic (ha), so it remains to be seen what will happen. If they are allowed to keep both parks within a given area, they could always do what Merlin has done in the UK, where it owns basically the three London parks and the further-away Alton Towers-Alton Towers gets to be the destination park, Legoland targets the kids, Thorpe the thrill seekers, and Chessington the kids too old for Legoland but not ready for Thorpe. That could work, but I have a hard time picturing that working out the same way in the states.