i have an idea!

So, everyone has the same question on there mind, right? How the crap are they going to kill the freaking devil if the colt wont work?!?!!!! well, ive heard some interesting theories like, Cass will kill him or dean will give in or they find some anciant latin spell to send him back to hell.
Well, im here to share my idea inwich i would like you to consider:what about the little boy? ya, know, the one that left for Australia or somewhere and is half demon and half human(i so want a cas action figure!). i think hes going to show up and somehow kill lucifer. but its just an idea. how they contact him and why the kid will help is beyond me. but as soon as i think of sothing else, i will let you know. what do you think?