Quick ramble:
ND's "ascension" is almost entirely based on quality of opponent these last 3 weeks (and this coming weekend). VA, GT, Stanford, and Navy all rank 112, 107, 92, and 91 respectively in scoring defense and all but Navy are ranked even lower in Total Defense YPG. The offense has looked better but the caliber of defenses they've done it against are at the opposite end of the spectrum compared to the CFP level teams. The same can be said for the defense. They've looked amazing, but GT, Stanford, and Navy rank 87, 106, and 114 respectively. Only VA ranks higher at 20, but ND didn't play against their starting QB. Again, the caliber of offense our defense would likely see (even in a NY6 game) is night and day. With that said, I feel it's always better to be playing your best football in November and that some of this success can carry over.
I'd also like to opine that a NY6 game against WF or Pitt puts ND in a scenario where they have nothing to gain and everything to lose. Idk if it's possible to land a more "reputable" opponent in this type of game, but ND winning a NY6 against a bigger name school carries more weight in the immediate and long term sense. I'd rather play Georgia. Just my .02
As far as the CFP goes, ND's ability to get in is possible. Honestly, the scenarios are endless. There are some really tough matchups looming and ND gets to sit back and watch it unfold. In dealing with 18-22 year old kids, anything is possible. Would anyone be shocked if Georgia finally beats Bama? Ok State and OU split? Cincy loses to Houston? UM or Wiscy beat OSU?