Temple left the MAC in June 30, 2012 to rejoin the Big East. While UMass joined the MAC as a football only member on July 1, 2012 and officially left on June 30,2016. It is worth noting that the MAC was in violation of the NCAA bylaws when Temple was a football-only member (2007-2011) and UMass was a football-only member (2012-2015) because the conference had 13 football member. Mathematically it is impossible for a division with 7 members to play a round robin division schedule and everyone play the same number of conference games.

WRT JMU, the DNR article came out in either the summer of 2012 or 2013. It was a series where the DNR interviewed both the President and AD on the current state of JMU athletics. In the article, JMU's AD said that JMU and Delaware had discussions with the MAC in the mid-2000s, but nothing progressed from it. In 2013, JMU did a FBS feasibility study that didn't give a recommendation one way or another about the possibility of switching subdivisions. The only thing it said was that JMU was "well-positioned for a potential transition to FBS." In 2014, the Sun Belt approached JMU about joining the conference. JMU said thanks, but no thanks because the Sun Belt doesn't help JMU's "recruiting goals" of regular students. Even ODU pushed hard for Conference USA to invite JMU to join the conference. JMU declined that offer and that spot eventually went to Western Kentucky. Here is an article I found from 2016 which asked the question why is JMU still competing in DI-FCS. The Richmond Times Dispatch wrote this article earlier this year. If you notice the only conferences that come up are the AAC and Sun Belt.

https://richmond.com/sports/college/as-another-wave-of-conference-realignment-begins-will-jmu-make-a-move-to-the-top/article_e1c63ac9-464b-5079-9113-6a40144ae9b5.html

In fact the MAC isn't even mentioned in the article. Now JMU may be having discussions with the MAC. However, I doubt those discussions go anywhere unless the MAC adds more teams in the Mid-Atlantic and New England regions. I doubt JMU has any interest in joining the Sun Belt because Appalachian State would be its closest conference foe and the conference doesn't help JMU with its recruiting goals. While the AAC would help JMU achieve that goal because Temple (full) and Navy (football-only) are already members of the conference. Plus, it is possible that the AAC will more members from those regions to replace the schools leaving to join the Big XII. If JMU is going to switch to DI-FBS, then my guess the AAC would be JMU's first choice.