Search traffic to social media sites will make Twitter and Facebook even more ubiquitous. Expect social media to be as indispensible as the phone. It already is for many. With a flood of traffic from SEs, it'll be impossible for web users to avoid social networks.
Search will eventually become personalized to each user based on their social media activity and friends' activities. All of the basics of SEO will still be important, but your social media presence will be a critical part of securing your search traffic.
I whipped up a few slides to explain how social media marketing and seo are colliding into one discipline.
Social media will most likely become just as important as content creation and inbound links for priming the SEO pump.