I lived in Florida before there were baseball teams there, thing I noticed was A. Native Floridians (read redneck kind that don't live in the big cities) do not, at large, follow baseball. B. The massive elderly community, which comes from every other state in the country, continues to root for the teams from their home states and visit them during spring training. So I really don't think there was ever a market for a Florida team, perhaps if they only had the Marlins and the Marlins were consistent, over the course of 50 years a new fan base would appear, but two teams with no payroll (Marlins go up and down like a roller coaster) in a state that doesn't like the sport/roots for other teams, just doesn't work.
I'm guessing Tampa gets shipped to another state one day and the only team that stay's is the Marlins (maybe, Marlins might go one day also).