Well, in the case of Notre Dame, they already have their program in place, it's just a matter of switching conferences...which would be a much shorter process than if a current team without a hockey program tried implementing one. I think PSU or Purdue would be the front runners to join D1 hockey, if it were to happen.
This wouldn't be a short process, it's still years off, but if the WCHA gets too crowded, and attendance starts to suffer slightly at programs that could sell out more games against bigger, more well-known rivals, I don't see how that process couldn't go through.