If ESPN can be satisfied, the deal could happen.
Per BYU's AD:
Big 12 decision last year was predominantly driven by ESPN.
"The national social issues (implied LGBT) were settled. That was a factor but the B 12 presidents were well beyond that and it was "absolutely not" what killed the deal. ESPN is a business and while the B 12 contract required them to pay, ESPN fought hard and was able to kill expansion.
BYU's relationship with ESPN has immeasurably elevated the prestige and standing of BYU sports in football, basketball, and all the other sports that have made noise in the NCAA postseason. "ESPN takes care of us." On the other hand, ESPN hated the idea of paying "$500 million more to the Big 12" and that was the dominant factor that killed the deal.
Moreover, Holmoe's plan B is still about preparing BYU for future P5 realignment, though it may be 5 or 6 years.
Wouldn't greatly surprise me if BIG 12 comes calling again before the next major realignment.