on FCS - yes, a number of schools have moved up. But in today's FBS climate, moving up is a much more expensive proposition.
for starters, the application fee for a school to move up is now $5-Million. and then you have scholarship requirements - moving from 63 scholarships to 85 for football, plus requirements that a school must provide a certain level of scholarships for other sports - and meet Title IX requirements.
then you have facility issues - going to a larger roster means you need locker rooms, meeting rooms, practice facilities etc that can accommodate more bodies.
it's a fairly sizeable investment. with proposals floating around for more compensation for athletes or potential revenue-sharing, some FCS schools may decide they're better off being a big fish in a little pond.