It really should end after the next series , but how ?
Well, if it was me, there would be a great big, high concrete wall that has been errected and that the Alexandrians come across. The remaining characters head for that, but are chased by a huge herd of zombies. The biggest herd they have ever come across.
Some are swallowed up by the herd and don't make it and die, others get over and it is ensured that Judith makes it over the top and to the safety of the other side.
Once over the other side of the wall the survivors see that there is in front of them, a perfect, fully functional city, like nothing has ever happened and it's still the days of pre apocalypse, so people, cars, buses, stores etc. Thousands of people and society all still in place and everyone dressed as they would have done before the zombie outbreak.
The surviving characters all exchange looks of astonishment. A military vehicle approaches and the survivors wait to be greeted and embraced.
The vehicle arrives, stops and soldiers get out. They immediately take Judith and then put the rest against the wall and shoot everyone else.
The end.