All NCAA scholarships are strictly one-year contracts, it is against NCAA rules for the scholarship to be good for more than a year (you resign every year) but coaches don't usually make that clear.
In gymnastics I think it is pretty rare for a school to take away a scholarship, as long as the athlete stays out of trouble/works hard/keeps the grades up.
I don't think gymnastics gives partial scholarships, but track does, and you'd better believe at most schools that if an athlete is recruited and given a decent-sized scholarship, they'd better be performing at a certain level after their first two years (usually give them a year to adjust) or they're going to get their scholarship reduced or even eliminated.
It's not a huge concern in the gymnastics world, but any gymnast thinking about competing on a scholarship should remember that it is a conditional year-to-year contract, and if they end up quitting or having major discipline problems they will lose it the following year. Not usually an issue for most gymnasts