Well, it looks like the debate is over... Britannica has announced a wiki overlay to its online presence.
"It's a bid by Britannica to remain relevant at a time when the world's most popular encyclopedia, the eight-year-old website Wikipedia, is written entirely by amateur experts. The new version of Britannica Online, set to debut this summer, will emulate the Wikipedia concept by letting subscribers make changes to any article, ranging from minor edits to near-total rewrites."
Hmmm... the shift. It's definitely happening. :)
BTW: I'm not sure about the "debut this summer" part. In my quick travels around the site, it looks like the wiki features are already there (for registered users) Must be in beta :)