Google’s dominance in mobile advertising in the U.S. will grow over the next few years as the market continues to take off, according to a new forecast from eMarketer, with the search giant claiming a whopping 55.7 percent of net revenues by 2015. Meanwhile, specific sites like Facebook and Pandora will see their share of the market shrink, eMarketer predicts, which would make sense as the overall mobile ad market begins to soar.

But the thing that really caught my eye from eMarketer is the prediction that Millennial Media’s market share will shrink from 2.3 percent in 2011 to a steady 1.2 percent this year, next year and in 2015. That share is significant considering how the mobile ad market will grow over the next decade or so, of course, but it’s a long way from the 15 percent the company reportedly claimed in 2010. So while Millennial still vows it will remain independent in a cutthroat space with a few massive players, I wouldn’t be surprised if it gets an offer shareholders simply can’t refuse in the next 12 to 18 months.