There are 15 current members as of Sept 1 2023:

• Boston College

• Clemson University

• Duke University

• Georgia Institute of Technology

• Florida State University

• North Carolina State University

• Syracuse University

• University of Louisville

• University of Miami

• University of North Carolina

• University of Notre Dame

• University of Pittsburgh

• University of Virginia

• Virginia Polytechnic Institute and State University

• Wake Forest University

FSU, Clemson, and UNC have expressed interest in possibly leaving the conference before the current TV deal ends (expiring in 2036). If any of these schools announce plans to leave the ACC before the beginning of the next academic/athletic year (we are using September 1, 2024), this market will resolve yes. No, otherwise.
Clarification: "Announce plans" means they have come to an agreement with the ACC to leave and pay the exit fee or some other agreement. Filing a lawsuit they could lose doesn't count. But they do not have to actually leave by September 1, they can just announce by then.

Stanford, Cal, and SMU are not yet members so they will not count for this market.