It has been more than ten years since Google made links the key ranking-criterion – since then, a lot has happened: PageRank lost some of its significance in the mix of signals, while other factors like “trust” or “link-diversity” probably gained some. You can file pretty much all of these measures under “fine-tuning” – there have not been any fundamental changes in all this time. Getting some fresh wind into the searchmarket would probably be a good thing though and might shift market-shares more towards a fair competition. At the moment, I can make out three possibly directions in which things might progress:

Links stay as main ranking-criterion – things stay the way they are. The Linkgraph still is the primary signal and changes will only happen in how it and other partial aspects are weighted. Google's ability to keep up and even expand their qualitative headway against their competitors in the past few years strengthens this possibility. It does not seem as if there will be an end to this development, with new patents from Mountain View going in the same direction.

Semantics finally make a breakthrough – for years we have announcements of the huge breakthrough being right around the corner, while nothing really happens. Wolfram|Alpha did not herald in a new age, Powerset became part of bing and seems to have gone under. If there was a real innovation here though, I think that a semantic analysis of websites could give us high-quality ranking-signals and at the same time (at least partially) take over the role that links have at the moment.

Socialgraph as a counter-draft – when Facebook let its link-button out into the wild a few weeks ago, it might have caused a stir in other sectors but it does not seem as though the knowledge of a possible impact on the searchenginemarket has not quite reached Germany. Basically, this system – like links – deals with recommendations: Person A recommends URL B. Additionally to that, the Socialgraph has a few advantages: it seems as though thanks to lower “participation-obstacles” you get more data (a blogposting here gets maybe 50 likes but only 2 to 3 links) and the recommendations could be weighted in a way that takes into consideration the relationship between the recommender and the recommended.

Personally, I think we will live with the Linkgraph as primary ranking-criterion for a while longer. The quality of the results has increased over the past years and is still being worked on. I think the Socialgraph is really interesting, but it will be some time before we will see the first uses and results.