What will be hot and what won't be in social media marketing for 2015? It's that time of year and everyone is publishing their thoughts online, but let's go beyond opinions and conjecture to look at some facts based on user behavior.A bit of digging revealed some great predictions about which social media sites will be worth your time for promoting your Authoritative Content in 2015. First, Mike Corak and Benjamin Pressman of Ethology provide some predictions related to Facebook, LinkedIn, Twitter, Pinterest, Google+, Instagram, Snapchat, and Vine that are worth reviewing.In their Top 8 Trends in Social Media for 2015 presentation, they note that all of the social media channels mentioned above are positioned well for continued high performance in 2015 except for Twitter, Snapchat, and Google+. Here are the details:Facebook is the number one social media site for referral traffic, social logins, and shopping influence. It's also experiencing growth in video content. LinkedIn is the number one social media site for B2B and is responsible for nearly 2 out of 3 (64%) social visits to corporate sites. One out of three professionals have a profile. Pinterest is number two for referral traffic and drives the most revenue. Instagram has fantastic engagement rates, and Vine is growing through its integration with Twitter.On the other hand, Corak and Pressman explain that Twitter and Snapchat aren't necessarily on decline in 2015 but Google+ will be due to its unclear importance. Twitter's growth is slowing while Snapchat has an high engagement but has its own clarity problems.You can follow the link above to see the full presentation. The predictions start to build a case for focusing on Facebook, LinkedIn, Pinterest, Instagram, and Vine in 2015 depending on your target audience and the type of content you publish.In his Top 7 Social Media Marketing Trends that Will Dominate 2015 article for Forbes, Jayson DeMers also tackles some specific social media sites in his predictions. Here are the details:Google+ will begin to fade away in 2015 while LinkedIn will become the priority for B2B. Instagram will become the high priority for image-based social media marketing with DeMers predicting, "We’ll see Instagram begin to outpace Vine as we enter 2015."You can follow the link above to read DeMers' full predictions for social media marketing in 2015.What do you think? Are you planning to adjust your social media promotion for your content in the new year based on 2015 social media marketing trends and predictions?Image: Nikllok licensed CC BY 2.0