It all depends on whether Wiki is covering its expenses or not. If they aren't, then it's just a matter of time until they eventually fold, at which point it's anyone's guess what happens to the website, trademark.
It depends in part on the details of how they are structured / chartered.
Any non-profit can wrap up operations and sell it's assets on the open market, but in most cases under US law, the proceeds would have to be donated to another non-profit.
In can be more complicated with an older non-profit because there used to be some options that don't exist any more.
For example, the corporation that owns Green Bay Packers football(American) team is chartered not under US federal law, but under Wisconsin state law as a non-profit stock corporation, an option that was removed from Wisconsin state law before WWII.