Its quality-centric so don't think a high playercount will keep you there
As I understand the PWA will be the judge on quality and thus will determine those that remain available to everyone. Those that don't meet those expectations will have to survive on thier money until they can fullfil them and will only be available to paying users. Does this make better sense? This entire system, in my opinion, is to give PW developers an incentive to do better than the cliched norm which would be making a server like Classic (not saying Classic is bad) and adding in personal modifications. It basically forces developers to push thier limits to create quality content to stay on top. It will be very rewarding for those that do so because they'll have a 'free' ride for that time being.
So it kind of goes without saying that ~75%-85% of the registered and paid servers will wind up dropping off after a while simply because all that is being done is pumping money into a blackhole.