Laser thingy need Satellite...mean its need complicated equipment and big effort.
If Ritsu's Parents use data that she acquire during her stay in Class E to create the Laser Thingy, then it impossible for the Laser to be deployed in earlier chapter
Even if the Author want to milking this series, the said "Deadline" to kill Koro sensei and class E to graduation already just couples of minutes away. So it will end soon.
Well, not like Author cant give a plothole to create AC season 2 though
IMO:
If Author want to create season 2,it not so difficult. Just look..
1. Laser thingy leave nothing but non Tentacle matter (clothes)
2. Shiro's Pet already inside, ready to be roasted in place of Koro Sensei
3. Class E , Bitch and Karasuma can just nod if asked that the Target dies or not
4. Koro has Ultimate Defense form (ball like), just hide in someone mouth
5. Koro himself is smart,I wont be suprising if he secretly discovered how to return to human form because of Okuda chemical experiment on him (incase the Ultimate Defense form cannot withstand the Laser)
6. The Tentacle it self is not explained yet, it respond to it host wishes, may be including Survival ? like...division of body? where little part will grow save from destruction ? you know..like Groot in Guardian of the Galaxy movie ending