I think the biggest opportunity with Wikipedia, rather than social integration (which happens a surprising amount on my Facebook and G+, much to my delight), is semantic search and display.
Wikipedia's goals in the past five years, in my opinion, have been revolving around the desire to amass as much knowledge and meaningful content as possible -- which they've done to a rousing success. Now I think it's time for them to consider systemic ways of paring and presenting that content in ways that carry meaning and urgency in a way that reading a 30-page article about Roman antiquity doesn't.
