Only once in the CFP era have there been 3 unbeaten teams in the CFP, that being last year. There has never been 4 undefeated teams. In fact, in 4 of the 5 years, there has been at least 3 one loss teams (and one year all 4), and only once has the Champion been undefeated. Only once has the Committee taken two teams from one conference.
There is no reason to think the Committee or History will be any different this year. ND is in perfect position. They are the highest rated 1 loss team. If they win out, they will get in. This weekend was the first of many Top teams playing each other - and upsets to come. If you think South Carolina/Georgia is the only big upset this year of a top ranked team - you haven't watched much college football.