I don't know what happened to the old wiki; I guess whoever put it up decided they didn't want to host it anymore.
I'm the one currently hosting the wiki. It's costing me less than $0.50 / month to host the thing, so I see no problem with just leaving it up forever. If for whatever reason I'm no longer able to host it, I'll make sure to preserve the information for the community so it stays accessible (that is, assuming an Aquaria modding community even still exists by then). Not sure what form that preservation would take; we'll figure that out if we get there.
I guess the short of it is, don't worry about putting content on the wiki because it's not going anywhere.