Nah, I believe they showed tons of blips on their little radar thing that could potentially be metahumans. And even if it didn't, there are hundreds of thousands, if not millions, of people in that city, and at any point they can decide that one of them suddenly discovered their powers late in the game. It's basically an unlimited supply if they want it.
Hell, how many people were there in Smallville, compared to how many got "meteorite powers"? If Smallville had been a city of any real size there would have been millions of them running around!