For comparison sake:
Georgia Tech (urban, shares city with NFL team)
Total students: 20,720
Stadium Capacity: 55,000
Northwestern Univ (urban, shares city with NFL team)
Total students: 16,640
Stadium Capacity: 47,130
Univ of Minnesota (urban, shares city with NFL team)
Total Students: 51,611
Stadium Capacity: 50,805
Univ of Buffalo (same conference, shares city with NFL team)
Total Students: 28,192
Stadium Capacity: 31,000
Toledo (same conference)
Total Students: 23,336
Stadium Capacity: 26,248
Temple
Total Students: 36,915
Stadium Capacity: ???
Average attendance in 2009: 17,379
NCAA attendance report
Based on students and other stadiums I was going to guess 40,000, but after seeing the attendance, I'd say probably closer to 30,000 with the ability to expand to 40,000.
(combining my interest in college football and philly developments into one post :-))