Assassination classroom has a interesting problem. Maybe...

I just started Assassination Classroom (finished episode 9 ) and I'm worried of the end. The only two endings possible would be the death of koro-sensei or the destruction of the earth. The second seems highly unlikely so the death of koro sensei is imminent. They could chicken out and have a happy ending but that would almost seem to stupid. A sad ending in going to happen and I'm not super excited to get there.