What do you think the name of the next expac could be?

[Mixt]

Final Fantasy XIV: Terminus?

[Keening noises from below]

[MoonPhaseAlpha]

FFXIV: Return (seriously?!) to Stormblood

[TheMightyMollusk]

Final Fantasy XIV: The Quest For More Money.

[Quintalian]

This is a good question! The pattern behind the expansion names seems to be color based. Heavensward was 'Blue Skies of Ishgard' in Japanese, Stormblood was 'Crimson Liberators,' and Shadowbringers was 'Pitch-Black Villains." So, with blue, red and black, it'd make sense for white to be the color of 5.0, as OP suggested, especially if we're going to Garlemald with its Ivory Standard. I also imagine that wrapping up the Ascian/Zodiark story would figure into the title somehow.

Oh, but it also has to have the initials S.B. for optimal confounding between previous expansions?

How about "Starblight"? It brings to mind the distant, dim white of 'starlight' while also conjuring images of the ever-looming threats of the already-crumbling Empire under Zenos, and the Ascians finally summoning their god and unmaking the world as we know it. And it does the S.B. thing.

[Crushnight]

Hmm..

SinisterBrood
SunBound
BrightSeeker
ShallowBeast

[Ashennae]

I'm guessing an Allagan/Dragon/Meracydia focused expansion myself, considering Yoshi P suggested we brush up on our HW lore for the next expansion.

Do you have a source for that? All that I remember is that we'd have quite a bit of a mess to come back to. Something we'll probably see in 5.4 the aftermath of.

[Soge01]

- The Return of Light

- Rise of the Booty Warriors

[Anienai]

-The Emancipation of Veruca Salt.

[CrispyUnicycle]

the next expansion will be split into two
final fantasy 14: red edition
final fantasy 14: blue edition

[Morningstar1337]

ARR aside, the titling convention seems to be a one word quasi-portmanteau of two thematic words. So my guesses are.

1. Mythmaker(s): Tying into this being the end of the Zodiarc and possibly Garlemald conflict, and thus the formative legend of the Warrior of Light of the Seventh Dawn
2. Steeldusk: A more pointed reference to Garlemald's role and their technological leap to everyone outside the Ironworks.The Dusk part alludes to that they oppose the Scions of the Seventh Dawn.
3. Godhunters: Referring to Zenos' desire to "hunt" for a worthy opponent and his design son Zodiark. And for a double meaning, your Primal slaying tendencies.
   • Primalhunters: Derived from the above but with the added meaning relating to knowing of a specific ancient (as in "primal") era.
4. Dawnbreaker: Like Mythmaker this alludes to this being the end of the WoL's formative legend, but unlike Mythmaker, it instead frames it as the end of of the current forces of Darkness (in this case Zodiark and Garlemald) and thus the break of Dawn. Also adds a parallel to ARR's themes of rebirth and light returning.

All of these also don't have any words used in previous titles for a bonus.

Regarding the Color theme of the Japanese titles. I think the following would be appropriate.

1. End of the Gray Hunters: Referring to Zenos, and again the steel motif. Steeldusk would be the likely localisation
2. Yellow Sun(rise): Referencing Azem, as the Sun is both yellow and rises (and it also brings to mind Japan's etymology). Dawnbreaker would be the likely localization.
3. God-Shattering Yellow Stars: Why yes we could do with Three Houses references :P. Again using yellow, this one would refer to Zodiark's end and Azem's symbolism. Godhunters/Primalhunters would be the likely localized title.
4. The Tales of the new Green World: playing off the XIII saga's intended name, as well as the fact that this is again, the end of the current conflict. Mythmaker is the likely localization.