That was the only thing that made me wonder if they'd kill Negan. They had already foreshadowed the cell, but if he's kept in a cell then the group can't stray very far. And having a mobile prisoner in a zombie apocalypse would be a huge pita.
I guess they could still have one group splinter out and look if they wanted to go that route.
I'm thinking that such an excursion would be made by a small number of the group.
Judging by what I saw in that last episode, you've now got over a hundred people in each of several locations - Sanctuary, Kingdom, Hilltop, Oceanside, and Alexandria.
I would expect a much smaller, expeditionary group to make the trip, rather than everyone leaving their current settlements.
I think it would also allow for more character development being separated than all bunched up together. I feel that the current cast is far too bloated. Characters come and go for weeks or months at a time with nothing to say or do.