Sirrian gave this answer about Puzzle Quest mini-games. Apparently, he doesn’t like poker machines so it’s not a good news for this kind of mini-games.
And there were/are so much topics about mini-games without any reply from the devs… Last mini-game was released so much time ago (I don’t remember when Treasure Hunt was released…).
So I don’t think we will ever have a new mini-game… It could be very interesting to know why devs did this choice.