Hi, and welcome!
The plan after October is done is to continue on with the Inktober52 challenges, which involves a weekly prompt, rather than a daily one. I've signed up for the Inktober newsletter via which they propagate the prompts, but haven't received an emails yet, so I'm not entirely sure when exactly the prompts will go up, but that is the plan.
So, post-October we will continue with the last weekly prompts of 2024, and then begin with the new 2025 Inktober52 list as the prompts are revealed weekly. The hiding the prompt and guessing sound a bit difficult to pull off as it would put up extra obstacles to participating, and would presumably quash participation, but it's a decent suggestion that we can keep in mind for when we've grown more active as a community. :)