No one can accurately predict success. Not specialized forums, not specialized workers in the field, and not even VCs whose sole incentive is to make money by investing in great ideas.
Even YC says as much that they have no clear idea as to what will be a success, and their strongest signal is the strength of the founders, and that there should be co-founders. I'm not sure how their experiment went with inducting people into YC just based solely on who they were, without an idea, but that's just further evidence that even people obsessed with finding success basically have no clear idea or signal as to what makes a success.