How I interpreted the ending
First few times seeing 31, I always saw the ending as...
In the film, Malcolm McDowell's character is undecided on what to do with Sheri Moon's surviving character. We then cut to her walking down the road, Doom-Head pulls up in his van, gets out, approaches her, she balls her fist, he draws his knives & smiles.
I figured McDowell had ordered Doom-Head to retrieve/kidnap Sheri, bring her back to the facility so they can start the process of brianwashing & training her into becoming a new 'Head'. It's hinted earlier in the film that the other Head's were previous victims-turned-villains. So I thought an idea for a sequel could be Sheri being turned into a mentalcase in preperation for the next '31', only for on the day, her to turn the tables on her captors, save the new batch of victims and wipe out all the antogonists, climaxing in an actual fight to the death with Doom-Head.
But I just listened to Rob's commentary and I was wrong lol Doom-Head kills Sheri right there & then. Whoops.
Still hope we get a Doom-Head spin-off movie at some point.