You know, I remember going to Six Flags Over Texas about 20 (or more) years ago. At that time, it was a lot closer (no, I'm not trying to really say it had the same things, but it was a lot closer) to a Disney park than the current one is. That is, it had lands with attractions that fit a lot closer to the theme of the lands. There was at least a coherent theme that you felt all the way through the park - you actually felt a (remote) connection to the influences on Texas as you went through the park. Over time, though, they lost this - started putting in different types of attractions, removing shows and small details, taking away the lands and theming, going for the latest and greatest coaster, with only minimal theming. Now, it resembles nothing like what it once was. I still enjoy going (I love roller coasters), but as far as any of the sense of theme that Disney has, it has really gone down from what it once was. It's a great example of how slow steady cuts/compromises can ruin an idea.
Really, I can't see any reason why Disney would want to buy Six Flags. They don't need the land in Texas (even were they to build a Texas park, they'd want much more land), much less parks all over the place to operate. They'd be unable to reuse most of the major attractions without major renovations (or a marked decline from even the already lower Disney standards). Plus, I though that the Six Flags corporation had tons of debt, which I doubt Disney would be wanting to assume.
I do hope the Six Flags chain turns around a bit - that would be nice on its own. But, I wouldn't expect any Disney corporate takeover anytime soon.