With the popularity I've heard of with the carolina railhawks soccer and the universities in the triangle area, its just a matter of time, right? So if an MLS team were to go into Carolina, what city do you think it would call home? My first impression would be near Raleigh, but I would have thought the same thing about any potential lacrosse team, which decided to call Charlotte home. I guess it comes down to the most loyal fanbase in the triangle, or the more proven major league market in charlotte.
In Raleigh (Cary) we have the Carolina RailHawks, which have a fairly large following. They are part of the North America Soccer League.
North Carolina isn't even in the picture for MLS expansion. They have a lot of other key areas of the country they would address first. If the Railhawks get enough of a following then MLS might consider absorbing them like they did with the Impact, Sounders, etc. but for now there are a lot more fruitful areas. Having the universities in the triangle area is not a big selling point because college students either won't have money for season tickets or will attend their school's games since they would be on campus. UNC is a perennial NCAA champion so they would be competing with a college for fans; probably not the smartest business plan.