I'm not sure Wikipedia needs a rebranding, and tell me if I'm the only one, but I use Google to get to specific Wikipedia articles. Wikipedia's actual search and search results need to be re-implemented, but I don't agree about redesign beyond that.

That leaves the actual articles. I like the way they are designed here, except for the monolithic nav bar.

If anything, this is a nice theme for articles - and theming is a feature that has existed on Wikipedia for a number of years now.