I don't think that link value will diminish so much it is the base of the whole internet, referencing googd resources. However I think that SE will be able to recognize interesting content from non interesting.
The problem they got in evaluating a site content is that they tried to recognize quality and original content. Actually I think they're boosting interesting content. All social media give information on what users like. I don't think google wants to show what HE think it may be the best content, but what searchers think is best. And why not use social data? Popular means the most liked content, so many happy users.
I think social media will start impacting a lot more in SERPs.