If Yui was able to get into Japan Women's University along with the rest of the band, Azusa would definitely follow her, so they'll only be separated for a year. I don't think this qualifies as Soul-Crushingly Depressing, so I removed it from the pool.
JuanValdezJr said: If "seniors must quit their clubs" didn't stop them, I don't think graduation will either. It certainly didn't stop the Lucky Star cast.
Though I admit I teared up when I got to Lucky Star's graduation scene. So I'll probably do the same for K-On.