Don't assume an undefeated Big 10 team gets in. Just a few years ago an undefeated SEC team got shutout & no one would have ever thought that would be possible. The Big 10's reputation is quite sour after their dismal performances in the last few title games. Their stock did not do better when they got trounced in the first major game of the year.
Looking at Penn St's schedule, they have played absolutely no one & the teams they did beat are not helping their case. Wisconsin is pretty much out of the running for the Big 10 title & they hurt Penn St when they lost to Michigan. Their only real signature win will turn out to be over Ohio State who is already looked down upon.
Now look at the possible Big 12 or SEC teams like Alabama, Georgia, Florida, LSU (even after the loss) or teams like Texas, Oklahoma, Missouri (even after the loss), Texas Tech, etc...
Those teams all have to face each other but the thing is most will be highly ranked at the time of the meeting. Lets look at Texas who I feel will lose next week against Missouri. They could lose & imo still have a better shot at getting a title berth over an undefeated Penn St.
For example they have Missouri next week will probably be in the top 10 or just outside of it at game time. Even before that game goes, they already have a more significant win over a #1 than Penn State could say the entire season. This is before they still get a top 10-12 Missouri team, a top 10 TT team, a possible top 10-12 matchup with Oklahoma State & the Big 12 championship game.
The same exercise could be said for the other Big 12 contenders. The same for SEC teams who will have more significant wins. I could even see USC getting in before they do.
Penn State will need help to get to the title game this season. Being undefeated won't cut it for them.