It would be interesting to see what would happen with an MLB team in Charlotte.
The biggest markets without a team currently are (in order of size): Orlando, Sacramento, Portland, Charlotte, Raleigh-Durham, Indianapolis, Nashville, Salt Lake, Hartford, Columbus, Greenville-Spartanburg, Austin, Vegas, Grand Rapids, Harrisburg, Jacksonville, OKC, Birmingham, Norfolk, Greensboro, Albuquerque, Louisville, New Orleans, Memphis.
A lot of those are consolidated in the northern part of the southeast (for lack of a better term) with Charlotte, Raleigh-Durham, Nashville, Greenville-Spartanburg, Greensboro, Louisville, Memphis. The question is does MLB think there are enough fans in that region who would latch onto a team in Nashville or Charlotte, or do they think all of those people are Braves fans anyways and they'd be better off with a city like Portland or Salt Lake City that is much more isolated without any other big markets in the region.
A team in Charlotte likely draws fans from other reasonably large markets (Greensboro, Raleigh-Durham, Greenville-Spartanburg) whereas a team in Portland really just draws fans from Portland.
Speaking as a Raleigh-Durham native, it would be hard to see a team there. I'd never stop being a Braves fan, but I could definitely see myself getting more and more attached to a local team as I take kids to games and it becomes part of my life.