Do you think that the language change in Miami, Florida indicates the future of the United States?
I do not think that Spanish is about to become the most-spoken language in the United States. I think that people who worry about that are misreading the general trends that happen with immigrants to the US.
The assumption behind this concern is that Hispanic immigrants will not assimilate and become American. They will, instead, keep to themselves and remain Spanish-speaking. Over time, the thinking goes, the US will become a Spanish-speaking country.
I do not see this happening. Immigrants who come to the US always learn to speak English because English is the language of economic opportunity and of power. Even if immigrants themselves do not learn English, their children do because that is how to fit in to the larger culture. Even in parts of America where the population becomes more Hispanic, English will remain the most spoken language.