I solely use the ROMHacking forum on PokeCommunity, and rarely post anywhere else. If implemented right, I think the wiki would be one of the best things to happen to the ROMHacking sub-community here. My only concern would be that it morphs into the Scrapbox's revenge. And I've made my opinion known how much I hated that spam filled death trap :P. There'd have to be a restriction on what hacks can be given a hack page and what can't. I'm not sure what atrocities the Game Development forum has seen, but back in ROMHacking, there've been quite a lot of spamming noobs who think that turning a sign into a talking tree automatically makes them hacking gods. That's my main fear regarding the wiki from a ROMHacking prospective.
However, I think the potential for this project far outweighs the risks. It's impossible for a hacker (or a game developer I'd imagine) to remember all the techniques they need to use all the time. I often find myself pouring over the Tutorials section so I can find that one simple little thing I forgot how to do, which wastes a lot of time. With the wiki, any additional ways to make a change could be documented on its page, and a convenient and easy to read list could be made of all the tutorial articles. There wouldn't be as much clutter either, seeing as I sometimes find myself going through several pages to find an addition to a tutorial or something.
It'd be the same for hacks. All updates would be in an easy to find place on their hack page. Instead of going through six pages of "GG don't quit" and other words of encouragement that you're not interested in reading just to find all the updates and screenshots, everything could be found on the hack's wiki page. Discussion would still be done on the forum, but the wiki would put everything into an easy to find and easy to update format. Little changes not worth a post could also be documented on the wiki. The same would apply to tools.
A wiki would seem to be a natural step in the growth process of the ROMHacking community here at PC, and would benefit ROMHackers and newbies immensely.