Steve Jennings/GettyFacebook CEO Mark Zuckerberg is back in the building just in time for Facebook to release its Q4 earnings on Wednesday. With 2016 underway, investors will be itching for not only a recap of the quarter, but a look ahead at the new year. Instagram, video ads, and, to a much lesser extent, Oculus, are the three key drivers of the business that analysts from FBR Capital Markets, Bank of America Merrill Lynch, and SunTrust expect to see this year.