I don't think we're due for that yet. They seem to be working through them in sequence from the earlier styles.
If they continue with the approach they've had so far, I would expect to get the next three default styles in the list – if they're not skipping over any, that would be the thin pigtails, long hair with headband and the short choppy one; next after those is the twin plaits if they skip one of those. (And for the male counterparts, all the next few are similar description-wise, but Zephirin, Martyn and Guydelot, and a more combed-down one as the backup option.)
The other three would some kind of early unlockable styles from different sources – possibilities could be the Adventure hairstyle from GS, the wedding hairstyle, early Mog Station sets (perhaps Minfilia and Aymeric?) and Samsonian Locks.
I shifted to just reading the summaries ages ago.
Well, more exactly I couldn't watch the videos for a long time as I had limited internet and streaming chews up way too much bandwidth – but now that I can watch them, I've quickly concluded that there's rarely much value for how much time they take to go through things. If there's anything worth knowing, people will be talking about it.