1) Old Cubans are very heavy GOP, younger ones more Dem leaning. Old ones dying off from 2008..
2) Growing non-Cuban hispanic population
Looking at the map it seems like Obama did about the same as 2008 in Miami Beach, Coral Gables, Pincrest, Kendall etc but had a huge surge west of I-95 in places like Doral, Sweetwater, parts of Little Havana. Doral went from like 51-49 Obama in 2008 to 59-40 this time and Sweetwater from close to 60-40 McCain to a slight Obama win.
Got 2008 numbers from Dave's redistricting app.
http://www.miamiherald.com/2012/11/14/3097037/hialeah-a-rare-stronghold-for.html