Difficult for me to picture a wiki as a replacement for the database. It's probably better to give up on the feature entirely. It's not the same functionality, and wikis tend to be messy very quickly when they're managed by several people. We may as well use Wikipedia or Steam if that's just to get infos about a game, no need to maintain that ourselves.
When I was a newsposter, or even as a user, I was/am frequently using the database when I wanted to see details about a game, and more importantly, the related articles: news, reviews, … It's also used for the GotY, I don't see how it could be done otherwise to extract the stats.
But yep, the database looks like the most difficult item to integrate with existing solutions.
Maybe we can create the articles with the forum itself, which would look like what we currently have in the forums only (so not a big difference there). If the forum engine has enough features, there should be an API to extract thread titles of a particular forum, perhaps even an excerpt of the post itself, to show in a CMS block. It's a common requirement after all; I think I saw something like that with WP and wpForo but it may be limited.
Then tags could be used to define or refer to games. For ex. tags with the game name, associated with a "news" tag for a news article, "info" for the information about the game, "review" for reviews, and so on. That would make many tags, but would that be a problem?
Surely having a forum and a CMS that pulls info from it shouldn't give us frequent version conflicts. That's what many websites do, but the forum engine needs a good API (though a direct DB access might be a plan B, the forum DB structure is unlikely to change much).
I have no idea of the traffic we have.
EDIT: I get what you mean by using individual tools, @Ripper;. I'm usually following the same principle.
We just have to see if what's practical without losing the functionality, or as little as possible.