So far they've shown off the intro quests for four (ETA: now five) different Lives (classes):
1. Woodcutter (English)
2. Alchemist (German)
3. Miner (Traditional Chinese script)
4. Mercenary (Simplified Chinese script)
5. Chef (Korean)
I think they're due to show 3-4 more, and I'll update this as they pop up. They seem to be doing 1-2 a week.
Also a 4-minute showcase of the quick Life-change video, which seems to indicate you need to go to the guild only when you're starting a new Life?
In the 3DS game, you could use the basic functions of a Life without being in that Life (I admit that when I'm in Wizard/Magician, I tend to whittle down bosses with a great-sword from the Mercenary Life then use a wand) - you just missed certain advanced moves, some class-specific higher level tools (for example, the Fashionista's Needle could only be equipped when you were actually in the Tailor's Life), and the class stat boosts.
But in the video released today, a woodcutter seemed to insta-change into a carpenter? Interesting!
(I want to see - especially with the combat and gathering/crafting quick swap - how they handle armor. In the original game, my characters tended to be under-armored because I couldn't bother with switching to heavier armor when I was spending half my time being in crafting and gathering classes, which do not lend themselves to stronger armor.)
ETA: There are some small amount of voice lines - for example, the greeting the guild lady gives you. However, this does not seem to have been voiced in all languages. Western languages get the English-language lines, Eastern languages get the Japanese-language lines.
( Some musings on the intro quests so far )