I think this is a great idea. I do a lot of work in enterprise knowledge sharing, and have seen good results making closer ties between Q&A or forum sites and wiki-like sites.
I disagree that the sites have 'very different' intentions (see Jan Doggen's answer). The two sites seem well aligned in their broadest purpose — to help people learn about the world by finding answers to their questions.
SE can inform WP about the sort of questions people have about a topic. It's also conceivable that an interaction on SE could reveal a nice pedagogic analogy or illustration or reference that could improve a WP article. Most importantly thought, I think the SE community could help improve WP by augmenting articles to help answer a question, where this makes sense. The encyclopedia already informs a lot of answers (and questions) on SE — I bet it constitutes a third at least of the links. If a person has more to add to the WP answer, I like the idea that they could contribute that part to the WP article, and just point to it from SE. Assuming they can do this in line with WP's usual guidelines, naturally.
At least in geophysics, I find that a lot of WP articles are incomplete or missing completely, and this could be a nice way to augment the more technical content on WP.