More than likely PS will end because people want everything for free!
Everything on the internet is free except tangible downloads. Hosting isn't very expensive if not
free for forums. For a forum such as this one, it probably costs no more than 20 a month for the
forum section on the absolute high end.
The stuff that is expensive is the download section which eats up bandwith. That is what the gold membership -obviously- pays for and covers the cost. On average, I'd estimate ~$5 per gold membership per month. My assumption is based on the idea that people are more likely to sign up for longer terms simply because this is a hobby that lasts a lifetime, not a game that is old in 3 months. 4 gold memberships pay for the forum, and whichever other ones pay for the download section. Just on this page we have 3 gold members that total 19 years on this forum.
The last bandwith issue is the performance section, but people could just link to youtube/soundcloud instead of the site supporting a playback. Again, if it came down to preserving solely this forum, it could/would be free.