From past experience, planning for 30,000 simultaneous connections is in the right range. What they don't cover is peak association rate (how many people per second can associate to the APs and have the LWAPS/controllers not fall over. They also don't cover the connection rate (number of devices per second pulling and clicking through the AUP/whatever page). Simultaneous users is actually less of a problem than the rate at which those simultaneous users connect.