What happens in the Fall is irrelevant - rosters are set the day before that team's first intercollegiate contest. That being said, any scholarship recipent, regardless of playing circumstance, must be "counted". As to waivers, an SA "quitting" or otherwise leaving the team doesn't matter, as that has no impact on the current expenditure (scholarship). Waivers are generally granted for extreme (season ending) injury prior to the start of the season, and issues w/military service (recall of NG, for example). There's a powerpoint @ ncaa.org on D1 waivers, but (IIRC) there's something like 800 waivers granted for all sports at all levels (D1,2,3) per year. Also check out informedathlete.com - most info there is pretty good.
Hope that helps.