My guess is that they'll be for housing only. They already cut our inventory space in half to save memory and we're getting chocos, I don't see them adding more to a player's group.

I hope they do something cool that can add to other aspects of the game.

An idea of this would be:
  1. certain NMs can drop eggs
  2. incubator can be crafted or bought for your home or free company hq
    -incubator is synthed from parts made by different crafts (i.e. blacksmith/goldsmith/weaver all make a single part and carpenter synths the actual item)
  3. egg is incubated for a certain time until it hatches
    -can be a static time or vary depending on size of home
  4. after hatching the pet itself can roam your home but is not usable outside of it
  5. pets give unique boosts for members of that house/free company (example: behemoth gives all members of your free company crit rate +5 and 5% more gil from enemies)

Procuring an egg will involve you with a dungeon or NM, incubators will help make crafters money and add to the economy, etc.

And maybe one day you will happen across a golden chocobo egg...