There's not many 'large cities' left that could create enough demand and support of a relocating team.
Austin, TX was mentioned as a potential destination but I don't see that happening. Texans are locked in to the Rangers and Astros.
I could see Nashville as they continue to grow and more tech companies make that their home.
New Orleans? They support the Saints, maybe there's enough demand for baseball too.
Otherwise they may have to look international... PR, Montreal, Vancouver, Mexico City.
Baseball could actually make international work, especially to Mexico.Unlike football, you're there for several days.
The issue is that baseball already has a hard enough time wedging all those games into a normal year, I can't imagine having to schedule in the offdays required around travel to places like that.