That JMU is definitely going FBS is far from certain; and IMO is has nothing to do with academics, as has been posited ad nauseam by JMU posters over the years.

I believe that the real issue with JMU is money.

According to the State of Virginia 2012:
16% of JMU's tuition and fees were allocated to athletics.
Athletics generated less than 26% of the actual revenue needed to cover expenses.

JMU has an endowment om the low side for a university of it's size and geographic location; 66.978 million.
Much of JMU's older alumni are women, who historically are not big athletic donors.

JMU is located in an extremely small population area, which probably precludes a large quantity of corporate donations.
JMU's location is also problematic when it comes to event attendance from locals who otherwise have no connection to the university.
JMU has lost over 8% per year in football attendance since 2011.

While none of the above issues are unique to JMU nor insurmountable, I believe that the "bean counters", and faculty and staff are very concerned about the efficacy of FBS as it relates to money.

A possible example of JMU's financial anxiety:
The proposed new JMU convo, which was approved for bonds by the Virginia legislature in 2011. This has not been acted upon, and is rapidly approaching a time when the $88 million is no longer an accurate number, which could cause the legislative process to have to be revisited. It has been reported that JMU is now looking for private donations for the convo instead.

I have otherwise no inside information, but in Virginia the "books" of all state institutions are a matter of public record, as are the reports of the Virginia Joint Legislative Audit and Review Commission.