It was definitely a huge missed opportunity. It would have been awesome to see how the bros functioned without Noctis around, and how Eos slowly turned into the daemon-infested world it was 10 years later. And it would have been more bearable of a transition if there were more story to explain the timeskip.

Apparently Iris and Lestallum all had older models too, but they never made it to the final release.

Unfortunately this was just another idea in FFXV that wasn't fully realized in development. Rushed.