Thanks for supporting my work Sgiampa! I'm very happy you like the collection.
The direction of Minifantasy Collection is 100% in the hands of my Patrons. Every month, the Patreon community suggest themes and ideas for new packs. Then, those suggestions are voted in a poll. The most voted theme wins and I make a new asset pack.
Answering your question, I can't guarantee when a new Heroes pack will be made, but I know that in the community there is interest in more classes. I'm quite sure rather sooner than later this will be something arriving at the collection :)