I know WordPress has a plugin similar to what I'm looking for, you basically would write up several drafts and have an option to have them posted automatically at a certain date. This would come in handy for certain types of forums (daily trivia etc.)
Uhm, I'm pretty sure this COULD be done via the task system - but I'm not too sure. Obviously you would need to be online at that time for the task to be run.
Or you can add a field to the new thread page in which you can choose the date/time for the thread to be posted.
Then the forumdisplay/search/... pages should eliminate all threads of which the timestamp is after the current time. That way, the thread will show the second it's time to show it and no one has to be online. (Can be done with one little addition to the sql query)