Hmmm. I'd like to go again soon regardless of where they hold it but here's a thought. For Spring Fling to "settle" anywhere, the city/area has to promise more than just good baseball fields (how many were used this year for all divisions?) They also have to be able to handle track, softball, soccer, etc; players, coaches, refs/umps, parents, and fan accommodations; administrative details and guest services; and so on.
My vote, Nashville and surrounding areas. (Abovementioned colleges, expanding out to Volunteer State, Cumberland, and Lebanon if need be for baseball and/or track... although M'boro has its good points too.) I'm guessing there's a few soccer fields around too (Brentwood/Franklin or Hendersonville/Gallatin/Goodlettsville), softball fields (almost anywhere) and well, you get my point.
One downside of Spring Fling moving to Nashville would be visiting teams trying to deal with the continuing interstate construction (and that would put a crimp in my plan...)