The part of Florida that is growing the fastest is the area stretching from Naples to Fort Myers, along with the area north of Orlando (Orlando itself is a Pit). Most of these are folks from the Midwest. Of course, my parents live in Palm Beach County, aka Scarsdale South, AKA The Bagel Belt (where they live, Boca Raton, is the "buckle of the Bagel Belt") and there isn't a snowballs chance in hell that that area of the state will go GOP.
My take on Florida: The influx of midwesterners and conservative-minded transplants is counterbalanced by a continued influx of liberal New Yorkers, Puerto Ricans, and non-Cuban Hispanics (although the wealthy Colombians and Venezuelans are quite conservative). I think that it will remain slightly more red than blue, although it will never be as solidly Republican as Utah.
I live in the area that you call the fastest growing area. Unfortunately, it is not growing redder. Bush was a strong candidate in Fla. He had his brother in the governor's mansion, and his brother is quite popular here. They made it look redder, but the voters were not voting Republican. They were voting for Bush. The fact is that the majority of voters in my area are now registered as Dems.
In 2008, both of the Bushes will be gone, and there is really no other strong Republican candidate in the state, except possibly Crist, who might win the governorship in 06. Unfortunately, the Dems have equally strong prospects, including former (deceased) governor Lawson Chiles' son.
South Florida will go heavily Dem, no matter how you cut it. In the last election, a strong moderate GOP candidate, Mel Martinez, won the Senate by the skin of his teeth. But he was running against a very liberal female Dem candidate who had hired a terrorist to be on her payroll while she was the President of Florida So. University. Martinez should have won by much more, and did win primarily because of the overwhelming Cuban support in So. Fla., and the heavy investment by G.W. Bush.
Since there is not going to be a Cuban or a Bush on the GOP ticket in 08, I think it will be an uphill battle.