Sometimes it's government policies themselves that unbalance the market and allow the proliferation of monopolies. I'm not sure it's the case with Google, though. Would appreciate a comment from someone more informed.
Don't underestimate the EU though, given some of the ignorant tech regulation they've already passed, it could happen at some point.
As Bing has demonstrated, Google's dominance in search is a result of superior technology and a huge lead. Even a company with the resources of MS hasn't been able to do anything but follow behind and create almost good enough copies at each step.
Although to be fair that's what MS has always done so maybe a more nimble company might have a shot some day.
In the near future AI and machine learning coupled with computing advances could be a way into search for competitors if G doesn't get there first.