Xavier has the rights to block Dayton to the Big East, so unless concessions are made to Xavier in other areas, Dayton isn't going there.
SLU has wanted to go the Big East for a while and they check a lot of boxes as ephoops pointed out. The initial hold up from the conference was if the school would commit financially. This was a few years ago and at that time, SLU would've been last in spending. Thats was crazy to hear, considering I just assumed SLU was outspending DePaul. I'm not sure if spending is an issue now so we'll see.