2016 has been a great year for SEO and Google evidently, Penguin got updated and RankBrain went live.
Some of the most important points for 2016 SEO were:
Optimizing for website speed
Microformats, Microdata and Structure data - in essence, search snippet optimizations
User engagement content as well as the optimization of your own brand
Creating content that is satisfying for everyone, the goal of modern SEO is to think out of the box and anticipate user's intent
Plain old on-page optimization around keywords - despite RankBrain this was still relevant for 2016
Provide subjects that are closely related together as a suggestion
What SEO trends should we expect for 2017?
I believe is all about ROI in the end and although in the past there was a problem getting an exact number of ROI for SEO, I believe we now have sufficient tools and search engine knowledge to understand and interpret data correctly so we can maximize our SEO ROI to the fullest.