I too would love to know the answer to this. I absolutely love the game, but I feel like there should be a small expansion to add a few more spells and demons for more variety. Game mechanics-wise, I think it is fine the way it is and I hope they don't add any more rules or complicated mechanics.
If I had to guess, I'd say maybe they are waiting for Halloween this year, if they plan on any expansions at all.
We have material for expansions planned. New spells, almost 100% legendary (special) demons, etc. It depends on how well it does. So if ya like it, get the word out.