To Herve and the other poster that are questioning the wisdom of a move to FBS football by some schools, perhaps I can shed some light on this.
I'll compare three of the schools making the jump to show you why it might make sense for some schools and not others. South Alabama, Charlotte, and Old Dominion.
I'm an alum of both GWU and South Alabama. As you may know, South Alabama is one of those new FBS schools. From USA's perspective, I think it makes sense. First, USA has a place to play (and is in a conference that has already destroyed its' basketball product in order to become a FBS conference - and USA isn't getting a bid to a better basketball conference) in the Sun Belt. USA has a paid for stadium with very low rent (its a 60 year old stadium but hey - its virtually free - and it seats 40,000) so we don't have to spend 60 million for a new stadium (like ODU and Charlotte will need to do). USA has averaged 20,000 per game playing FCS and Division II teams, so we can break even. We have only one FBS school within a 3 hour drive and a football mad culture in our market. The Sun Belt is largely a 'bus' conference (its geographically tight) so travel isn't going to be a disaster. For USA, it was a no brainer and while not revenue neutral, it isn't as taxing as one might seem. For USA, the move makes sense. Sun Belt schools don't pay their football coaches 1 million per year. And the athletic foundation has paid for all the scholarships for 5 years in advance.
For Old Dominion, its a bit more complicated. They're going to have to spend 60 million bucks on a new stadium. They're going to have to compete with 6 AQ FBS teams (Wake UVa, NC St, Duke, Md and UNC) as well as East Carolina within a 3 hour drive. Their new conference will require tons of expensive travel for all sports. That being said, they have sold 10,000 season tickets (which isn't bad for a CUSA school). However, their basketball product will be playing a lot of utter garbage instead of in the CAA. Furthermore, football really isn't that popular in the Mid-Atlantic (even the AQ schools have trouble filling smaller stadiums during good years). Old Dominion football is going to be expensive, but they've made all the correct moves so far. Another issue for ODU basketball is that they've had some recruiting success in the Northeast. Those contacts will likely wither away. It might take them time to build new recruiting pipelines to replace the ones they'll likely lose.
For Charlotte, football is really going to be an expensive gamble. There's a LOT of football competition in the area. 2 SEC teams, and 4 ACC teams are within 2.5 hours. And Charlotte has a NFL team. They're spending 60 million on a stadium. They wont see much of an increase in travel costs for their olympic sports (as they had to do a lot of flying anyway). But their basketball product will be in a much lower profile conference. Without Memphis, CUSA will be a one or two bid league. They don't even know when the CUSA will let them join them for FBS football. Until then, Charlotte will be a FCS independent. So its going to be about 5 years before they can possibly make the jump. They've sold few season tickets. Their first season (as a transitional team - playing D2 teams) will be instructive. If the fans don't show up or Charlotte starts losing to Presbyterian, its going to be a long road.
For South Alabama, making the jump is low risk. For Old Dominion, its a medium risk (as they've already got a successful, albeit young, and well supported FCS team). For Charlotte, its bit more of a risk.