No, you'll still be unlimited as long as you maintain your existing plan regardless of your device. New/Added lines won't be eligible and changing your plan obviously loses the unlimited status.
Well this is where they will get you. A few years ago I had to change my plan because the plan somehow couldn't support a smartphone when I got the original Blackberry Storm. I am sure a year or two down the line everyone will have to change their plan resulting in no more unlimited data. -- Mets, Cowboys, Devils