What happens when the kids of Glee graduate?

I love glee it one of my favorite shows..the last episode wad kinda sad...mostly because they lost..but everything went out smoothly like fin and rachel get back together.santana and britany seem okay..and the weird..mercedes and sam okayyyy..and of course kurt boyfriend saying i love you..that was cute..but they are juniors now so next year will be their Seniors..what happens when they graduate..will they get an entirely new cast of talented kids idk.