I'd take the bet that it stays. No way you could plan a new convention for September at this late date.
Very difficult, but not impossible.
At minimum, they would have to accept a serious downgrade of accommodations in order to get it done. Even midsized cities have facilities capable of hosting the convention itself, but the hotel room demand pretty much limits the possible venues. Of course, given the crappy state of the economy, it might be far less than we think.
Then, you have demand for airline flights in and out of the city. Given the massive reduction in airline seat availability, this could be a big problem, depending on the venue. You will probably need a hub city for a major airline.
Throw in the demand for night life, dining, drinking and hookers and you limit it still further. And, since it is the Democrats, you would need more than just the heterosexual variety of hookers. Of course, some of these establishments are willing to follow the demand.
Yeah, the security arrangements would have to start over from square one, which is a non-starter. And after North Carolina taxpayers footed so much of the bill for preparations, they can write off that state for the next ten elections if they pull out now.