LSU made it in with 2 losses back in '07, and that was when you had to be in the top 2.
Rare occurrence obviously, but it can definitely happen.
That was the same year that Missouri and Kansas were numbers 1 and 2 going into their game. UCF, Boston College, and WVU were the top 5 late in the season as well. Had it not been for all of those teams absolutely crapping the bed in last half of November, OSU and LSU would never have played. That year wasn't just crazy, it was black voodoo magic levels of absurdity. Like Tennessee was seriously a couple of plays going differently away from being national champions....
As for the question of the OP, if there was a year where that scenario could happen this would be it. The last two years of the playoff? Not a chance in hell it was happening. But this year could very well produce a double dip from one conference, so why not a 2 loss team?
It isn't completely out of the question that Washington goes to sleep in a regular season game, and gets stunned in the PAC 12 championship game. And/or Houston lays an egg late in the season, like Boise St has done in years past. And/or Wisconsin doesn't lose another game until the B1G championship, producing a conference with 3 1 loss teams that look pretty darn good. And/or (and this is a big one) LSU absolutely plays to their full potential, and wins out. Alabama loses to Tennessee and LSU, A&M beats Tennessee but loses to LSU and Bama, and it ends up being LSU v Tennessee in the SECCG.
Doesn't matter who wins that, because if all of that plays out, or most of it, it will be time to grab the popcorn come selection sunday, and get ready to see the playoff instantly expanded to at least 6 teams for 2017.