If they add Ivalician Moogles to FFXIV, there's a perfect setup for their existence.

[Enkidoh]

If they introduce Ivalician Moogles as a race in the future, they can justify their existence by explaining that the legend of Good King Moggle Mog descending from the heavens was a tale distorted over the centuries.

It was actually a faction of Pommed Loporrits that left the moon for the surface in the distant past. Modern moogles are branch descendants of these Pommed Loporrits.

Many of these Pommed Lopporits would settle in Ivalice and go on to use their advanced knowledge of technology (and obsession with prime numbers) to construct much of the technology found in Goug.

It was already confirmed long ago (way back in HW in fact), that Good King Moggle Mog was actually a distorted cultural meme of Chieftain Moggle, the first chieftain of Moghome in the Churning Mists and a haphazard recollection of the transporter from there down to Mourn in the Dravanian Forelands (which moogles used to escape from Nidhogg's rampage to the surface).

SE have already stated in the past that there is no new playable races coming, so I think we can pretty conclusively rule out Ivalician moogles being added in general (given we already have actual moogles in the game), let alone a playable race.