They may save that for mid life of the show. If it lasts more than 3 seasons.
Perhaps, but I'm not so sure. They seem really committed to this 'realism' thing. And if they slow down and stop running through DC's villain's catalog they got more than enough realistic villains to last for a lot of seasons.
And even then, some of the superpowered villains can be 'logically' given scientific reasons for their extraordinary abilities.
Or they could just, you know, create their own original villains.