I seriously doubt you'll ever see any amusement park in either Broward or Dade county. For starters, it's pretty much land-locked unless you wanna build next to the Everglades, which would suck. Secondly, I highly doubt any city commission would ever aprove a proposal to do so. There's already too much else to do and spend your money on. Plus, they realize that Orlando has cornered the market, so there's really no reason to try and compete.
Don't get me wrong, while I lived there, I always wished for a Six Flags, but the closest we ever got was Six Flags Atlantis water park in the 80's, and then even that just faded into obscurity.
Hmmm, if anything, that's what needs to return to the region...a world class waterpark. That's something Boomers could really expand into. There's still plenty of room surrounding it, if memory serves me right.