I'm sure we're just going to be introduced to new characters. We already have Daryl's group, and then the abductor of Beth is probably not someone we know yet. The show is always going to maintain a dozen as the core, with several supporting actors.
Also, did anyone think that they maybe should have just left Lizzie there instead of killing her? Maybe that would make her a threat, or maybe she would come to Terminus and cause problems, but was that really the only way?