There was to have been a third season. And it was to have been awesome.
Also, Mon-El was supposed to be in the line-up for Season 2. Instead we got Superman X.
James Tucker had plans to make Alexis Luthor into The Dragon for Imperiex in season two. She would have later made a Heel-Face Turn (out of personal selfishness, of course) and betrayed him, gaining the galaxy's trust and running for a political position. Due to Executive Meddling, however, they had to reduce the number of female characters for most of the season, and the subplot was cut.