If you have lived in America for the requisite period and paid into the social security system, you are entitled to medicare at an old age, obviously as someone just retiring to Florida you would not be.

There is already a retirement visa, it is called the EB5 and leads to green card, just got to raise $500,000 to invest in a designated regional centre. With the increase in home values a lot of people are just doing that and can afford to. There is the alternative of E2. To be frank, living as I do at the moment in Gods waiting room of Portugal and being totally bored sick I think that making older people who want to live in the US run a business isnt necessarily a bad thing!!
Oh and for those who can afford to do so, snowbirding on B2 and six months in and six months out does hold many attractions as having the best of both worlds.