That will be a poll topic on my Subscribestar for the next update. The two villain masterminds or Saucertop characters from Monster Monsoon may get added. The v4 update could be the last one for this game, that's also something that will be determined by how popular the idea of extending this game is. Starting this year I will keep a roster of unused but popular character designs for use in my future projects, so if the villains don't make it in, they may appear in some other game at some point.