We knew Microsoft was phasing it in based on a variety of announcements over the last little while, including their highest profile XBLA game for 2013, Ascend, and the promotion they've given Happy Wars in Fall 2012. They've also done a bunch of F2P WP7 games and a few on W8.
The real problem is that there haven't actually been any console F2P successes. No one seems to have made a game design that "pops" the way some of the most famous F2P mobile games have.