Eligible immediately. And the beat goes on.
Sometime soon, giving redshirt years is going to go away at the mid-major level. It's not worth it to watch your better players leave.
But then people will find ways to graduate in three years.
The brightest ones may, and if they do, good for them. Most won't though, or that would be my guess.
Very, very few would be able to do this if they wanted to. Not many have what it takes to devote the time need to D-1 basketball, an extra-heavy course load, and summer school without getting so worn out that they would not be much good either on the court or in the classroom.