Content will remain king
Everyone is familiar with the phrase Content is King but what we need to keep in mind and focus on is that quality of that content. 2013 was a banner year for Google updates. They took making sure that content is and remains quality to a whole new level. With release of their latest update hummingbird they are reiterating the important of quality content within context.
Go mobile or die
Having a site that is user friendly on a mobile app will be imperative moving forward. Search engines are striving to improve user experience on mobile devices, determined to reduce load time to under a second. As the mobile search traffic increases so will their concern with showing user friendly content in search results and if your site is not then you better get with the program.
Understanding semantic search
Semantic search strives to understand the context and intent behind a users search queries. What this means is focusing on keywords in a body of content is less important than understanding what types of results are served for that keyword (ie, videos, news articles, images, etc). The goal will be to see what search engines are displaying and focus on creating that kind of content.
Get on board with Google+
There is a strong correlation with G+ activity and strong search results. Building your equity in Google+ by growing your reach, creating authorship and becoming an active member in the community will drastically help your search rankings and improve click through. The more you share and that content is recieved by the G+ community via +1s the better!
In summary, with all that said it will always remain important to remember the fundamentals of on page optimization. There are now many pieces to the SEO pie but on page optimization will always remain a large piece of it.