ND football will never join a conference. Pure fantasy to believe they ever will.
Your opinion. I think otherwise.
ND is excluded from the 4 team CFP format when they have one loss to an ACC/B1G/PAC school that did not play in their conference championship. ND would be passed over by a B1G Champ, the ACC Champ, the SEC Champ and the Pac12 champ, all with 1 loss because each of the champs had an extra game against a quality opponent. They may even be passed over by a 1 loss team that lost in a conference CG game. ND and its fan base will howl about how unfair it is. The rest of the country will shrug their shoulders and say go talk to Big 12 who got shut out because of no CG. It is the price of independence. Let it happen 2 or 3 times, and ND will suddenly want to be in some conference.
The way things are configured, ND will be at a disadvantage versus conferences with a CG. They will almost always be the outside of the top 4 unless they are undefeated. The 5 ACC games do nothing for them except fill out their P5 schedule easier. Without a chance to wipe out a loss in the ACC in a CG (in any conference, substitute a a loss to a B1G team if you want), they come up short.
And let's not forget that the P5's move to autonomy from the NCAA certainly weakens ND's voice in FB. I really don't think the ACC will do anything to enhance ND's chances when they are not a full member.
My guess, they go to the B1G in the next 5 years.