This is a pretty good article for fans like me who geek out at stats and tables and such. It breaks down the various potential candidates for future expansion, which is essentially every school in the P5 except the SEC schools which the SEC values (so not Vandy or Mizzou) and a handful of major G5 programs.
The categories are athletics, "fit," and market, and with this in mind, Notre Dame is in a tier of its own, while the next category are "no-brainers" which are Oregon, FSU, North Carolina, and Washington.