In GMU's Athletics and Recreation Master Plan, as part of the 2014 Campus Plan
http://facilities.gmu.edu/masterplans/athletics_masterplan_FEB05.pdf
they have a Stadium Option, Project 23 which is a 15,000 seat Football Stadium at an estimated cost of $69,000,000 dollars. The Stadium Project includes team offices, practice facilities and team lockers.
It would be built on the West Campus near the Braddock Road entrance that exists there now and that is slated for improvement as part of the Ox Road Bridge connecting the west campus to the main campus.
The entire Master Plan is 148 pages but it's worth a look to get an idea what the university has in mind. There's even mention of building a Minor League Baseball facility on the Shirley Gate Road property.
Realize that all of this doesn't mean they're going to build any of this but it isn't being ruled out and that they're being proactive in planning for their possibility.
The key parts are Development Options 1.5 and Capital Projects 1.6