So apparently there was a scene that was shot but not included that involved adult Judith and Rick Jr.. In the comics, Carl lives to be an adult, and we see how the world has moved on. Seeing something like this would have been an interesting (though, maybe slightly corny) ending.
The Walking Dead Series Finale Reveals Deleted Alternate Ending
Makes sense to not use that ending. It kind of interferes with the Rick/Michonne spin off, (or the other future shows) especially if they ever decide to do something else with any of those characters.