Texas wants the Big Ten, but the Big Ten won't take them as long as the Longhorn network continues to exist. The ACC wants Texas, and is willing to let them keep their network. Texas would rather be in the PAC 12, but the PAC 12 is asking for revenue concessions regarding the Longhorn network. Texas must decide which deal is better for them. That decision will set the rest of the dominoes tumbling.
Correct me if I'm wrong but I thought the Texas to ACC deal would be for all sports except football and Texas would become an independent. Same with Notre Dame. There really is no reason at all for the ACC to agree to something like that.