Mobile ranking data could see some changes in the coming months if Google rolls out the mobile search index. There are no definitive details yet but there is plenty of speculation. The mobile index will be updated faster and Google will be able to run their algorithms against this set in a more concentrated fashion. Page speed will likely be more important with this mobile index.
It was revealed that a link tagging system is employed by the Google search team. This includes labels for different types of links. This highlights how footer links may have a much lower value than links in the actual content. He mentions that they have tons of link labels that they utilize, including a Penguin real-time label. If they see that most of the links are Penguin real-time, then Google might take a deeper look and see what the site owner is attempting to do.
Speculation around whether Penguin uses any kind of machine learning has been rampant since the recent real-time update. This was put to rest as Gary Illyes confirmed it does not use any type of learning via Twitter. Machine learning has gotten quite the buzz since RankBrain was incorporated into the Google algorithm.