Big 10 POV- New Big markets to network, expands south into area with a growing population.
ACC Schools POV- Alot more money when the BIG renegotiates in 2016, if this happens the ACC will cease to exist so no buyout. Also UVA/UNC would enjoy being part of the Big10 academia.
It's superficially logical, but it's very strained. They aren't all that south really, just kind of on the edge there. The new TV markets they would be opening up aren't particularly impressive. The biggest catch is that none of them are good at football and that's the impetus behind all of this change. Add four east coast northern south football mopes? 
18 million people live in NC and VA...thats alot of people that will would now need the BIG network.
Also you dont see any teams that are actually "Good at football" Making conference changes. Excluding WV(big12 is different model than other conferences with networks) when was the last time a team that moved from one BCS conference to another(NU,MU,CU,AM,PITT,SYRACUSE) actually won a conference title?
I'm not sold that any of it will happen but the underlying circumstances for it to happen are there.