Really I don’t see Yoshi and the development team ever bothering with such a feature now – players asked about it way back in Beta and they basically said “no” as it is adds little to nothing to gameplay and just wastes player time for the development and system resources required to be spent on it. Also Eorzean airships (namely, the Bronco- class ships) operated by Highwind Skyways are far far smaller than the Vanad’diel airships and are definitely not designed to feature as zones (they look more like flying taxis than actual ships).
And one of the major peeves of mine about FFXI’s airships with the ‘real time flight’ aspect was they ran to strict timetables, and there was nothing more infuriating than missing an airship or ferry by the skin of my teeth and then having to wait a frustrating long time for the next one to arrive (like, up to nearly an hour of real time at least in some cases, like with the ferry) – at least here airships only depart when you board them so leave that nonsense behind in the past where it belongs. With FFXIV-style teleporting between homepoints being added in FFXI now (complete with ffxiv gil cost) and the result of airships barely seeing any use at all now in FFXI it’s clear even SE themselves regard the concept as outdated.
Finally it’s highly likely we will not be visiting a new continent for quite a long time yet (we still have one Eorzean citystate to visit, namely Ala Mhigo, which is strongly hinted to be the city we will be travelling to in the next expansion) so even if SE did decide to add this for ‘international’ airship flights, it won’t be added any time soon I’m afraid.
Those train tracks are not as long as they seem, they only run between Castrum Centri in Mor Dhona and Castrum Meridanium in Northern Thanalan – they don’t run anywhere else (it’s little more than a glorified conveyor belt). Given you already use the tracks on foot as the zone line between the two zones, there is zero use or need for the player to actually travel on it – unless, it was used to access say Castrum Centri as an actual dungeon in the future. But that is highly unlikely.
Now Ul’dah’s separate railway on the other hand I can definitely see being used for players as an extra mode of transport in and out of the city, similar to the ferries used in Limsa Lominsa and Gridania… but alas, given the backstory of the railway that Lolorito has been deliberately stonewalling Nanamo’s attempts to open the line up to passengers (to prevent competition to his lucrative chocobo haulage business), alas I don’t see this sadly happening either.