I think the best solution is to release the first version and only scratch the surface about the marketplace. Do not directly hint about it. Maybe the early fee

I think the best solution is to release the first version and only scratch the surface about the marketplace. Do not directly hint about it. Maybe the early feedback of the first users will give you an idea of whether they want a marketplace in the first place or other major design/market directions you might want to follow to please them before spending time and money on something you're probably unsure will work.