... if I had to draw conclusions based on what we have in the game files, I'd say that the Dance Studio will let players create custom dances by combining different moves, effects, and modifiers. Once they are happy with their dance, it looks like they will be able to name it and share it with other players (it would explain the dancecache.wdb to store them clientside). The PlayDance("dance name") command most likely means that players will be able to save multiple dances on a character and pick one depending on their mood.MULTIPLE DANCES! (Probably.)
SHARED DANCES! (Most likely.)
SPARKLY EFFECTS IN DANCES! (Perhaps?)
This poses a new social issue. If you can share dances and you spend hours designing a perfect dance just for your character and some level 12 shows up and says "I CAN HAS DANCE?!" -- what do you do?
Say it with me: "L2Create, Nub."
I think it could be like a bit like gold begging -- people who didn't grind all that gold out on their own don't see the big deal of asking for a handout. And people who don't have the energy or creativity to make their own dances will likely ask to use other people's, if sharing is allowed.
I suggest that (as long as it isn't super-expensive per dance) everyone make a dance that you're willing to hand out to others, but you keep your favorite for yourself. There's no shame in not giving away your hard work, as long as you're polite about it: "Sorry, I made this specifically for this character and don't plan to share it. I do have another dance I can share, though."
That gives them a chance to use your other dance (and see you as a generous person) or be a whiny jerky brat and keep demanding the one they asked for (we've all seen it with gold beggars).
Luckily, whiny jerky brats aren't our problem and give us a chance to exercise our Ignore list! :D