Free calling: just when will it happen?

As Gmail users would know, a feature allowing you to call people inside of Gmail was recently introduced. This must be the first step towards something crazy- free calling. Currently, this feature does not let you receive calls, but who knows? It soon could. Gmail calling is free in the U.S. and Canada. Which leaves us with one question: When will a feature like that hit mobile phones? On iOS products you can make calls for just $10 a month using apps like Line2, but free calling has not happened yet. What if free calling did hit mobile devices? That would certainly change the world of cell phones. The other question is if that will cause Google to get a monopoly on operating systems. Say Google put free calling as a feature on its Android OS. Would you even think about getting a non-Android phone? No! So why would anybody else? That would mean that everybody would switch to Android. But why are we assuming that only Google would make free calling? In order to stay in the game, other companies would HAVE to put free calling on their operating systems. And then, poof! It would be a free calling world.