ND will not join a conference until they have no path for making the playoff without being a conference member. So unless the committee that picks the teams passes a rule that only teams that play in.a conference are eligible, ND will stay an independent.
The committee that picks the teams?
It’s not up to them.
The Big Ten and SEC hold the power to change the CFP's format for 2026 to 2031, effectively neutering the other FBS conferences and Notre Dame.
Would they find a horsetrade that involves ND being forced to the BIG? In a two party system, it’s not inconceivable they find such a resolution
Come 2032, when the CFP and NCAAT deals are up, who knows what college football looks like, let alone the CFP.