Quote from SuperCreeperGirl
EDIT: just thought of something!
Look at this Q&A. I've underlined the part I'm talking about.
Can I charge access to a specific part of my server, such as a minigame or world?
No, you cannot charge for any part of a server other than the initial access. Once on a server, all players must have the same gameplay privileges. You may make a different server for the user to connect to which features “premium” areas, and charge for access to that server instead, but the benefits cannot carry over to your other servers.
In other words, if you wanted to have a perk (such as a minigame) that can only be used by people who pay hard currency, you could just make a new server with the premium perks, and then give people the IP (via a plugin or something) whenever they donate the required amount of money. All you would have to do is make sure that the perks on the premium server don't cross into the main server.
No idea if this is allowed, but it would work. (I don't own a server myself, so I really don't know if this would be executable, though I think it would be. Just saying)
Woah. This is probably the most useful contribution on the whole thread. Basically you can have a "trial server", and then if you like it enough, you can donate to move to the one with more features?
In general, I don't think the "good" (large) servers will die. I think they will innovate. If they can't, they didn't deserve to exist (at least that's what Mojang is saying).
The donators having powers to give everyone something is a really neat idea, as well.