I don't know why people thought ND was going to join full time before the recent NBC extension. ND has always told everyone who was around since 1995 that football was never going to join any conference. People just kept refusing to believe them for some reason, I guess.
ND has no reason to join the ACC in full for football for any reason, ever, even in 2027 and beyond. They have everything they want right now, exactly the way that they wanted it.
Basketball, baseball, lacrosse, soccer, etc...in a great conference with the ACC.
Hockey in a great conference in Hockey East (with NBC Sports agreeing to televise every ND home hockey game).
Playoff access, the NBC deal, Orange Bowl/Fiesta and other "BCS type" bowl access and schedule control over seven games a year as a football independent.
Five football games (will help with late Oct. and Nov. scheduling) and minor bowl access with the ACC. This affiliation will help more with Southeast exposure and recruiting.
Access to the discussed future ACC Network as a conference member. ND is in a secure conference now with the GOR.
Some people thought that the new playoff format and conference realignment would work against ND. They were wrong. ND is set up nicely.
Why change anything? The only thing possible is if the playoffs stay only at four teams and the rule becomes conference champs only. Does anyone think that likely?
Finally, the ACC likes the ND partnership. It is not going to be issuing any ultimatums to ND.