They actually announced v20 earlier this week. I am keeping a close eye on the official pages at the moment and I am going to update you guys in this thread when I find more info.
I think on Sunday they changed the News Banner on the official Korea Page
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to say "Flyff version 20 update comming soon", sadly it just links to the main homepage.
And for tomorrows patchday (korea patchday = thursday) they are doing an 9 hour maintenance from 10 to 19 o'clock (1am to 10am GMT).
Patchnotes say:
- Valentines Day NPCs removed
- Preparation of the v20 update part 1
< Additional information will be posted before the actuall update >
- v20 event starts (probably some kind of event to get ppl pumped up for the update)
Official News Link:
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That is all the information there is at the moment.