I personally wouldn't want to dump all of the information on it (but there are definitely useless pages. A page that lists the contents of each VOL isn't really that useful).
All of the information can be migrated.
The question is mainly this:
What do you want to do with the wiki SYSTEM itself? (not the content on it)
Currently there are really 3 suggestions / choices:
1. Keep everything the way it is (continue to use MediaWiki)
2. Move everything to the main site (yes, it has a complete user-access system and a WYSIWYG editor, see the below picture).
3. Switch to a completely different system totally.
Regardless of what we do, it is absolutely essential that we improve the quality of information available. There are many useless pages, and many incomplete pages. Things need to be organized and the useless pages trashed.
Here's a screenshot of the site editor:
It's hard to say if an easier editor would get people interested in working on it. Like garrett said, perhaps we could offer some sort of incentive to get people to work on it either cleaning it up or adding more information.
Personally, I think #2 is the best option because then it puts all the information all into one place (and yes, the main site does allow people to log in and edit, the controls for that are just completely hidden until you are logged in. It also tracks changes and allows reversing the changes just like the wiki).
Putting everything in one page seems best for new users, that way they don't have to search everywhere to find out what they want to know.