Maybe the last scene will be Cooper arriving in Twin Peaks. This would guarantee a season 4.
shareI've been pondering this same scene in my head, what if Cooper only wakes up at the end of episode 18, as a sort of parallel with the end of season 2? That'll piss off a lot of people.
shareI think it has to end with Good Vs Evil, so there will be something really bad happening, maybe several Lodge spirits trying to possess the folk in Twin Peaks, especially Bob trying to possess Becky, and to fight the evil, Cooper will finally wake up and make his way there in order to prevent it, together with Cole and Tamara Preston, and also Laura Palmer will 'protect' them and play a big part of the finale.
I'm sure they'll keep an open ending so they can do a 4th season sometime.