Article from Deadline has a small hint that Dean will be in more than just the Supergirl pilot:
Deadline interview The relevant excerpt:
DEADLINE: One thing that is similar in several of your shows is casting actors who have either played the role before or have a strong previous connection to it, like Lois & Clark’s Dean Cain. Why do you like to do that?
BERLANTI: It’s fun. It’s one of the real nice benefits of doing the job that you get to work with people like John Wesley Shipp, and Mark Hamill, and Dean Cain, and Helen Slater. Part of the fun of making these things is actually that we’ve enjoyed other incarnations of them. So, it’s part homage and it’s part a celebration of the property, and a celebration of the characters. With Dean and Helen in Supergirl, we have some good storylines for them this season too.
